Evidence behind Replenish

Where the literature allows, Replenish grounds its recommendations in meta-analyses, systematic reviews, or large randomised controlled trials. These are the highest tiers of evidence available in nutrition science, because they synthesise findings across multiple studies and are less susceptible to the errors and biases of any single trial. Where this level of evidence does not yet exist for a given question, we use the next best available methodology and say so clearly.

Nutrition science is complex, contested, and constantly evolving. Rather than cherry-picking studies that make our product sound impressive, we cite evidence to explain the choices we made, and we tell you honestly when that evidence is strong, mixed, or limited. Where small sample sizes, conflicts of interest, or methodological limitations exist, we flag them openly. We think you deserve that.

Our approach to evidence

Calories

Population formulas carry meaningful individual error. Your calorie needs change every day, and a well-designed target should reflect that, not ignore it.

What The Evidence Says:

The accuracy limits of energy prediction equations. The Mifflin–St Jeor equation,¹ validated in a 1990 study of 498 healthy adults, remains the most accurate widely-used formula for estimating resting metabolic rate, outperforming the previously dominant Harris–Benedict equation. However, the validation data itself showed that even this improved equation produces meaningful individual-level errors. The UK Scientific Advisory Committee on Nutrition² used doubly-labelled water (the gold standard for measuring free-living energy expenditure) to establish population-level Dietary Reference Values for energy, and was explicit that these values carry significant individual variability. Their conclusion: DRVs are population averages, not targets for individuals. For a given person, formula-based estimates can be off by several hundred kilocalories per day even when all inputs are accurate.

Energy expenditure is not fixed, and neither is appetite. Total daily energy expenditure shifts continuously in response to activity, sleep quality, stress, hormonal cycles, and dietary history. Research consistently documents that metabolic adaptation occurs during calorie restriction: the body reduces expenditure beyond what is predicted by weight loss alone, a well-replicated phenomenon in the literature. A calorie target set at the start of a journey will progressively overestimate needs as adaptation occurs. Food is woven into every part of daily life: celebrations, social occasions, tiredness, stress. Eating naturally varies day to day, and a useful calorie range should accommodate this variation rather than frame it as failure.

Calorie restriction and micronutrient gaps. A 2024 study by Fulgoni et al.³ modelled the nutritional impact of calorie reduction in over 6,000 US adults with overweight or obesity using NHANES dietary data. Even a 20% calorie reduction significantly increased the proportion of adults falling below estimated average requirements for Vitamins A, C, D, E, and B6, as well as calcium. At 50% reduction, shortfalls approximately doubled across most nutrients. This study helps support Replenish’s decision to track 9 micronutrients during calorie restriction.

Is a calorie surplus necessary for muscle building? A 2019 narrative review by Slater et al.⁴ concluded that adequately trained individuals with sufficient protein can achieve lean mass gains in energy balance or a modest deficit, though a small surplus is thought to optimise the rate of gain. A parallel-groups trial by Helms et al.⁵ compared small (~+358 kcal/day) and large (~+756 kcal/day) surpluses in 21 resistance-trained individuals and found no significant difference in muscle outcomes, but greater fat gain in the larger surplus group. The n=21 sample means firm conclusions are not warranted, which reflects the broader state of this literature: high-quality trial evidence on optimal surplus size remains sparse.

How this applies to you?

Lose Weight - A moderate deficit supports fat loss while minimising the metabolic adaptation that makes aggressive deficits progressively less effective. Large deficits carry a documented risk of micronutrient inadequacy: Fulgoni et al. found that at 50% calorie reduction, shortfalls across vitamins and minerals nearly doubled compared to unrestricted eating. This is why Replenish tracks nine micronutrients alongside calories, so reducing intake does not come at the cost of nutritional quality. Because individual responses vary considerably and energy needs change as weight is lost, recalibration against actual logged intake is more reliable than maintaining a formula-derived static target.

Build Muscle - For many people, a small surplus of around 100–300 kcal/day is likely to be enough to support muscle gain, while limiting unnecessary fat gain. Larger surpluses tend to produce greater fat accumulation rather than proportionally greater lean muscle gain, as the additional energy beyond what muscle protein synthesis can utilise is stored as fat.

Track My Health - UK Dietary Reference Values for energy are population-level estimates with known individual variation. For general health, calorie ranges function as a reference for understanding intake patterns. They are not a goal to hit or a limit to stay under.

Conflict of Interest: Fulgoni et al. (2024)³ was funded by Abbott Laboratories, a supplement manufacturer. The micronutrient gap findings are consistent with independent literature on calorie restriction, but this funding relationship is worth noting.

Small Sample: Helms et al. (2023)⁵ enrolled only 21 participants. Findings on surplus size and muscle gain should be interpreted with caution until replicated in larger trials.

    1. Mifflin, M.D., St Jeor, S.T., Hill, L.A., Scott, B.J., Daugherty, S.A. and Koh, Y.O. (1990) A new predictive equation for resting energy expenditure in healthy individuals. The American Journal of Clinical Nutrition, 51(2), pp. 241–247. doi.org/10.1093/ajcn/51.2.241

    2. Scientific Advisory Committee on Nutrition (2012) Dietary Reference Values for Energy. London: The Stationery Office. gov.uk

    3. Fulgoni, V.L., Agler, A., Ricciuto, L., DiFrancesco, L., Williams, D. and Hertzler, S.R. (2024) Impact of simulated caloric reduction on nutrient adequacy among U.S. adults with overweight or obesity (NHANES 2015–2018). The Journal of Nutrition, 154(9), pp. 2732–2742. doi.org/10.1016/j.tjnut.2024.07.022

    4. Slater, G.J., Dieter, B.P., Marsh, D.J., Helms, E.R., Shaw, G. and Iraki, J. (2019) Is an energy surplus required to maximize skeletal muscle hypertrophy associated with resistance training? Frontiers in Nutrition, 6, p. 131. doi.org/10.3389/fnut.2019.00131

    5. Helms, E.R., Spence, A.J., Sousa, C., Kreiger, J., Taylor, S., Oranchuk, D.J., Dieter, B.P. and Watkins, C.M. (2023) Effect of small and large energy surpluses on strength, muscle, and skinfold thickness in resistance-trained individuals: a parallel groups design. Sports Medicine - Open, 9(1), p. 102. doi.org/10.1186/s40798-023-00651-y

Protein

The UK baseline is designed for basic adequacy in sedentary adults, and current evidence suggests that many active people or those pursuing fat loss or muscle gain may benefit from higher intakes.

What The Evidence Says:

The UK reference intake and its limits. Public Health England's Government Dietary Recommendations¹ set the Reference Nutrient Intake (RNI) for protein at 0.75 g/kg/day for adults, commonly rounded to 0.8 g/kg/day, a figure established to meet the needs of 97.5% of sedentary adults. This is the value displayed on UK food labels. However, the RNI is a minimum adequacy threshold for a sedentary population, not an optimal intake recommendation for people who are physically active or who have specific body composition goals. The International Society of Sports Nutrition's position stand² recommends 1.4–2.0 g/kg/day for exercising adults, approximately double the UK baseline.

Protein during fat loss. When calories are restricted, adequate protein serves two critical functions: preserving lean mass and supporting satiety. A randomised controlled trial by Longland et al.³ assigned 40 young men to either a lower-protein (1.2 g/kg/day) or higher-protein (2.4 g/kg/day) diet during a significant calorie deficit, with both groups following an identical exercise programme. The high-protein group gained 1.2 kg of lean mass while losing 4.8 kg of fat; the lower-protein group lost 0.1 kg of lean mass while losing 3.5 kg of fat. A follow-up study by Ogilvie et al.⁴ in a calorie-restricted population confirmed that higher protein intake not only attenuated lean mass loss but improved overall dietary quality. The higher-protein group consumed more vegetables, fibre, and micronutrients as a consequence of food choices, reinforcing the connection between protein targets and food quality more broadly.

The protein ceiling for muscle building. A 2018 meta-analysis by Morton et al.⁵ (49 studies, 1,863 participants) used meta-regression to examine how muscle hypertrophy and strength gains scaled with protein intake during resistance training. The analysis found that gains in fat-free mass plateau at approximately 1.62 g/kg/day, with a 95% confidence interval upper bound of 2.2 g/kg/day. Beyond this, additional protein intake did not produce statistically significant additional gains in lean mass. This finding was confirmed in a dose-response meta-analysis by Tagawa et al.⁶ across 74 RCTs. Importantly, both reviews concluded that intakes above the ceiling are not harmful for healthy individuals. Returns simply diminish rather than reverse.

Plant versus animal protein. Reid-McCann et al.⁷ conducted a 2025 systematic review and meta-analysis of 39 RCTs examining whether protein source affects muscle mass, strength, and physical performance outcomes. No significant difference was found between plant and animal protein when total protein intake was matched. This finding has direct relevance for Replenish's user base, which spans omnivore, vegetarian, and vegan dietary patterns.

Long-term health and mortality context. Large prospective cohort analyses by Naghshi et al.⁸ and Huang et al.⁹ , collectively covering over 700,000 participants, found no consistent association between higher protein intake and increased all-cause, cardiovascular, or cancer mortality in healthy adults. Kidney safety is a genuine consideration for those with pre-existing renal disease, as evidenced by Ko et al.¹⁰ and Mantzouranis et al.¹¹, which is why Replenish displays safety caveats in the app for users who flag kidney conditions.

How this applies to you?

Lose Weight - Higher protein intakes (1.2–1.6 g/kg/day or above) during a calorie deficit are well-evidenced to preserve lean mass and support satiety, substantially above the 0.8 g/kg/day UK baseline.

Build Muscle - The Morton et al. meta-analysis supports approximately 1.6 g/kg/day as the practical sweet spot for most resistance-trained adults, with returns diminishing but not disappearing above this threshold. This is Replenish's default target for this goal, with the rationale displayed in the onboarding.

Track My Health - For general health with no specific body composition goal, the UK RNI of 0.8 g/kg/day provides a meaningful baseline for adults. Replenish displays this as the starting reference, while tracking intake patterns over time to identify habitual shortfalls or excesses.

    1. Public Health England (2016) Government Dietary Recommendations: Government recommendations for energy and nutrients for males and females aged 1–18 years and 19+ years. London: Public Health England. gov.uk

    2. Jäger, R., Kerksick, C.M., Campbell, B.I., Cribb, P.J., Wells, S.D., Skwiat, T.M., Purpura, M., Ziegenfuss, T.N., Ferrando, A.A., Arent, S.M., Smith-Ryan, A.E., Stout, J.R., Arciero, P.J., Ormsbee, M.J., Taylor, L.W., Wilborn, C.D., Kalman, D.S., Kreider, R.B., Willoughby, D.S., Hoffman, J.R., Krzykowski, J.L. and Antonio, J. (2017) International Society of Sports Nutrition position stand: protein and exercise. Journal of the International Society of Sports Nutrition, 14, p. 20. doi.org/10.1186/s12970-017-0177-8

    3. Longland, T.M., Oikawa, S.Y., Mitchell, C.J., Devries, M.C. and Phillips, S.M. (2016) Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss. The American Journal of Clinical Nutrition, 103(3), pp. 738–746. doi.org/10.3945/ajcn.115.119339

    4. Ogilvie, A.R., Schlussel, Y., Meng, L. and Shapses, S.A. (2022) Higher protein intake during caloric restriction improves diet quality and attenuates loss of lean body mass. Obesity, 30(6), pp. 1411–1419. doi.org/10.1002/oby.23428

    5. Morton, R.W., Murphy, K.T., McKellar, S.R., Schoenfeld, B.J., Henselmans, M., Helms, E., Aragon, A.A., Devries, M.C., Banfield, L., Krieger, J.W. and Phillips, S.M. (2018) A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), pp. 376–384. doi.org/10.1136/bjsports-2017-097608

    6. Tagawa, R., Watanabe, D., Ito, K., Ueda, K., Nakayama, K., Sanbongi, C. and Miyachi, M. (2020) Dose-response relationship between protein intake and muscle mass increase: a systematic review and meta-analysis of randomised controlled trials. Nutrition Reviews, 79(1), pp. 66–75. doi.org/10.1093/nutrit/nuaa009

    7. Reid-McCann, R.J., Brennan, S.F., Ward, N.A., Logan, D., McKinley, M.C. and McEvoy, C.T. (2025) Effect of plant versus animal protein on muscle mass, strength, physical performance, and sarcopenia: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews, 83(7), e1581–e1603. doi.org/10.1093/nutrit/nuae200

    8. Naghshi, S., Sadeghi, O., Willett, W.C. and Esmaillzadeh, A. (2020) Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. BMJ, 370, m2412. doi.org/10.1136/bmj.m2412

    9. Huang, J., Liao, L.M., Weinstein, S.J., Sinha, R., Graubard, B.I. and Albanes, D. (2020) Association between plant and animal protein intake and overall and cause-specific mortality. JAMA Internal Medicine, 180(9), pp. 1173–1184. doi.org/10.1001/jamainternmed.2020.2790

    10. Ko, G.J., Rhee, C.M., Kalantar-Zadeh, K. and Joshi, S. (2020) The effects of high-protein diets on kidney health and longevity. Journal of the American Society of Nephrology, 31(8), pp. 1667–1679. doi.org/10.1681/ASN.2020010028

    11. Mantzouranis, E., Kakargia, E., Kakargias, F., Lazaros, G. and Tsioufis, K. (2023) The impact of high protein diets on cardiovascular outcomes: a systematic review and meta-analysis of prospective cohort studies. Nutrients, 15(6), p. 1372. doi.org/10.3390/nu15061372

Carbohydrates and Fats

Low-carb and ketogenic diets can produce meaningful short-term weight loss. The evidence is consistent that over the long term, beyond 6–12 months, they offer no to little advantage over a balanced diet.

What The Evidence Says:

Short-term versus long-term: the critical distinction. Low-carbohydrate and ketogenic diets often produce faster weight loss in the first weeks to months, a well-documented phenomenon driven primarily by rapid glycogen depletion and associated water loss, combined with the appetite-suppressing effects of ketosis and higher protein intake typical of these diets. However, the authoritative 2022 Cochrane review by Naude et al.¹ (61 RCTs, 6,925 participants, follow-up periods of up to two years) found little to no difference in weight loss between low-carbohydrate and balanced-carbohydrate diets when studies were examined beyond the initial phase. When trials lasting 12 months or longer were analysed, the apparent advantage of low-carbohydrate diets disappeared. This is one of the strongest syntheses available on the question, and it suggests that long-term outcomes are driven more by adherence, calorie balance, and protein intake than by carbohydrate restriction alone.

Meta-analyses on ketogenic diets specifically. A 2013 meta-analysis by Bueno et al.² (13 RCTs, 1,415 participants) did find that very low carbohydrate ketogenic diets produced slightly greater weight loss than low-fat diets over 12+ months, though the absolute difference was modest (~0.9 kg). Silverii et al.³ found low-carbohydrate diets were effective for long-term weight loss in people with obesity, but noted that adherence declined significantly beyond 12 months, a consistent pattern across the literature. An umbrella review by Patikorn et al.⁴ covering 34 meta-analyses confirmed that ketogenic diets reduce body weight and waist circumference but found no consistent advantage over other dietary patterns for long-term weight maintenance, with some studies reporting elevated LDL cholesterol in subgroups.

Ketogenic diets and muscle building. For people whose goal is building muscle, carbohydrate restriction introduces a specific and well-evidenced trade-off. Henselmans et al.⁵, a 2022 systematic review of 24 crossover and parallel-groups trials, found that higher carbohydrate availability improved resistance training performance across acute and chronic study designs. Muscle and liver glycogen are the primary fuel sources for high-intensity exercise; depleting them constrains training output, which constrains the training stimulus that drives hypertrophy. This is reflected directly in the hypertrophy data: Vargas-Molina et al.⁶ found in a 2022 meta-analysis that ketogenic diets produced significantly less muscle mass gain compared to non-ketogenic diets in resistance-trained individuals. Figueiredo and Cameron-Smith⁷ further examined whether carbohydrate availability directly modulates muscle protein synthesis post-exercise and concluded it does not. The implication is that the carbohydrate effect on hypertrophy operates through training performance capacity, not anabolic signalling directly.

Dietary fat and long-term mortality. The carbohydrate question cannot be separated from its fat corollary. A large prospective cohort study by Shan et al.⁸ (37,233 US adults, 15-year follow-up) found that both very low carbohydrate diets and very low fat diets were associated with modestly elevated all-cause mortality compared to moderate, balanced dietary patterns. It’s important to note that this a cohort study which assesses correlation and not causation. The finding held after adjustment for lifestyle confounders. UK government guidance⁹ does not recommend restricting fat to extreme levels, but emphasises substituting saturated fats with unsaturated fats and limiting free sugars, a quality-focused rather than ratio-focused approach.

How this applies to you?

Lose Weight - Low-carbohydrate diets can accelerate weight loss in the first 4–12 weeks, but this advantage attenuates over time and disappears beyond 12 months in head-to-head trials against balanced approaches. Replenish defaults to a balanced macro split because it is the most consistently sustainable pattern in the long-term evidence, without precluding lower-carb approaches for users who prefer them.

Build Muscle - Carbohydrate availability directly supports training performance and therefore the stimulus for muscle growth. The evidence for ketogenic diets and hypertrophy is unfavourable. Adequate carbohydrate intake alongside sufficient protein is the evidence-aligned default for this goal.

Track My Health - UK guidance focuses on dietary quality markers, fibre intake, free sugar limits, unsaturated over saturated fats, rather than a specific carbohydrate or fat percentage. Both extremes (very high fat, very low fat) carry long-term mortality associations in prospective data. A varied, balanced diet is the most defensible default.

    1. Naude, C.E., Brand, A., Schoonees, A., Nguyen, K.A., Chaplin, M. and Volmink, J. (2022) Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk. Cochrane Database of Systematic Reviews, 1(1), CD013334. doi.org/10.1002/14651858.CD013334.pub2

    2. Bueno, N.B., de Melo, I.S.V., de Oliveira, S.L. and da Rocha Ataide, T. (2013) Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomised controlled trials. British Journal of Nutrition, 110(7), pp. 1178–1187. doi.org/10.1017/S0007114513000548

    3. Silverii, G.A., Cresci, B., Benvenuti, F., Sanchez, A.M. and Mannucci, E. (2022) Effectiveness of low-carbohydrate diets for long-term weight loss in obese individuals. Diabetes, Obesity and Metabolism, 24(8), pp. 1458–1468. doi.org/10.1111/dom.14709

    4. Patikorn, C., Saidoung, P., Pham, T., Phisalprapa, P., Lee, Y.Y., Varady, K.A., Veettil, S.K. and Chaiyakunapruk, N. (2023) Effects of ketogenic diet on health outcomes: an umbrella review of meta-analyses of randomized clinical trials. BMC Medicine, 21(1), p. 196. doi.org/10.1186/s12916-023-02874-y

    5. Henselmans, M., Bjørnsen, T., Hedderman, R. and Vårvik, F.T. (2022) The effect of carbohydrate intake on strength and resistance training performance: a systematic review. Nutrients, 14(4), p. 856. doi.org/10.3390/nu14040856

    6. Vargas-Molina, S., Petro, J.L., Romance, R., Kreider, R.B., Schoenfeld, B.J., Bonilla, D.A. and Benítez-Porres, J. (2022) Effects of the ketogenic diet on muscle hypertrophy in resistance-trained men and women: a systematic review and meta-analysis. International Journal of Environmental Research and Public Health, 19(19), p. 12629. doi.org/10.3390/ijerph191912629

    7. Figueiredo, V.C. and Cameron-Smith, D. (2013) Is carbohydrate needed to further stimulate muscle protein synthesis/hypertrophy following resistance exercise? Journal of the International Society of Sports Nutrition, 10(1), p. 42. doi.org/10.1186/1550-2783-10-42

    8. Shan, Z., Guo, Y., Hu, F.B., Liu, L. and Qi, Q. (2020) Association of low-carbohydrate and low-fat diets with mortality among US adults. JAMA Internal Medicine, 180(4), pp. 513–523. doi.org/10.1001/jamainternmed.2019.6980

    9. Public Health England (2016) Government Dietary Recommendations: Government recommendations for energy and nutrients for males and females aged 1–18 years and 19+ years. London: Public Health England. gov.uk

Exercise

WHO recommends 150–300 minutes of moderate aerobic activity per week, plus muscle-strengthening on two or more days.

What The Evidence Says:

WHO 2020 Physical Activity Guidelines.Bull et al.¹ published the peer-reviewed summary of the WHO's 2020 guidelines in the British Journal of Sports Medicine, synthesising evidence from hundreds of studies across populations and age groups. The guidelines establish that adults should accumulate 150–300 minutes of moderate-intensity aerobic activity per week (or 75–150 minutes vigorous-intensity), and should perform muscle-strengthening activities involving major muscle groups on two or more days per week. These targets are described as thresholds above which a substantial proportion of the physical activity-related health benefits are realised. Importantly, the guidelines also state that any amount of physical activity is beneficial compared to none, including activity that falls short of the full target. Replenish uses these WHO thresholds as the foundation for its exercise guidance across all goals, with the specific balance adjusted according to what the evidence shows for fat loss, muscle building, and general health respectively.

Aerobic exercise dose-response and fat loss. Jayedi et al.², a 2024 dose-response meta-analysis of 116 RCTs and 6,880 participants, quantified the relationship between aerobic exercise volume and body composition outcomes. Body weight, waist circumference, and body fat percentage all decreased in a dose-dependent fashion up to approximately 300 minutes of moderate-to-vigorous aerobic exercise per week, closely tracking the upper bound of the WHO target range. In this meta-analysis, more clearly clinically meaningful fat-loss effects tended to emerge from around 150 minutes per week and increased further up to about 300 minutes. Notably, the gains from each additional 30-minute increment diminished progressively. The greatest return on time invested occurred within the WHO-recommended range.

Comparing exercise modalities for body composition. Lafontant et al.³, a 2025 systematic review and meta-analysis, directly compared resistance training, aerobic training, and concurrent training (both combined) for body fat outcomes in healthy adults. Concurrent training produced the greatest overall improvements in body composition: it outperformed resistance training alone for fat loss and aerobic training alone for lean mass preservation. This supports Replenish's recommendation that most users benefit from including both modalities rather than specialising exclusively in one, with the balance determined by the primary goal.

Resistance training volume and hypertrophy: the Schoenfeld evidence. Schoenfeld, Ogborn and Krieger⁴ conducted a dose-response meta-analysis examining the relationship between weekly resistance training sets per muscle group and muscle hypertrophy. Across 15 studies, the analysis found a clear and statistically significant dose-response relationship: performing 10 or more sets per muscle group per week produced significantly greater hypertrophy than fewer sets, with less than 5 sets per week representing a low-stimulus threshold. Crucially, the response was not linear indefinitely. The evidence supports meaningful returns up to around 10–20 sets per muscle group per week for most individuals, after which the marginal benefit decreases and recovery demands increase. This study is directly foundational to the resistance training volume guidance Replenish uses for muscle-building users, as it provides quantitative benchmarks rather than qualitative recommendations alone.

Muscle-strengthening activity and long-term health. Momma et al.⁵, a 2022 meta-analysis of 16 prospective cohort studies and nearly 1.5 million adults, found that muscle-strengthening activities were independently associated with lower risk of all-cause mortality, cardiovascular disease, total cancer, diabetes, and lung cancer, even after adjusting for aerobic physical activity levels. The association with mortality reduction appeared strongest at around 30–60 minutes of resistance exercise per week, though this comes from observational data.

How this applies to you?

Lose Weight - Aerobic exercise produces dose-dependent fat loss up to ~300 minutes per week. Resistance training is a critical complement: it preserves lean mass during a calorie deficit and prevents the disproportionate muscle loss that occurs with cardio-only approaches. Jayedi et al.² and McCarthy & Berg⁶ together form the evidence basis for both halves of this recommendation.

Build Muscle - Weekly resistance training volume is the primary driver of hypertrophy, with Schoenfeld et al. providing the quantitative framework: 10+ sets per muscle group per week is the evidence-supported threshold for meaningful gains. Aerobic activity is included to support cardiovascular health and recovery, not at volumes that impair muscle protein synthesis or total training capacity.

Track My Health - WHO guidelines form the direct reference point: 150–300 minutes of moderate aerobic activity and two or more muscle-strengthening sessions per week. Even partial adherence to these targets produces significant risk reductions for cardiovascular disease, diabetes, and all-cause mortality relative to inactivity.

    1. Bull, F.C., Al-Ansari, S.S., Biddle, S., Borodulin, K., Buman, M.P., Cardon, G., Carty, C., Chaput, J.P., Chastin, S., Chou, R., Dempsey, P.C., DiPietro, L., Ekelund, U., Firth, J., Friedenreich, C.M., Garcia, L., Gichu, M., Jago, R., Katzmarzyk, P.T., Lambert, E., Leitzmann, M., Milton, K., Ortega, F.B., Ranasinghe, C., Stamatakis, E., Tiedemann, A., Troiano, R.P., van der Ploeg, H.P., Wari, V. and Willumsen, J.F. (2020) World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British Journal of Sports Medicine, 54(24), pp. 1451–1462. doi.org/10.1136/bjsports-2020-102955

    2. Jayedi, A., Soltani, S., Emadi, A., Zargar, M.S. and Shab-Bidar, S. (2024) Aerobic exercise and weight loss in adults: a systematic review and dose-response meta-analysis of randomized clinical trials. JAMA Network Open, 7(12), e2452185. doi.org/10.1001/jamanetworkopen.2024.52185

    3. Lafontant, K., Koltun, K.J., Lovalekar, M., Bird, M., Dunn, A., Foulis, S., Charkoudian, N. and Nindl, B.C. (2025) Comparison of concurrent, resistance, or aerobic training on body fat loss in healthy adults: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition, 22(1), p. 2507949. doi.org/10.1080/15502783.2025.2507949

    4. Schoenfeld, B.J., Ogborn, D. and Krieger, J.W. (2017) Dose-response relationship between weekly resistance training volume and increases in muscle mass: a systematic review and meta-analysis. Journal of Sports Sciences, 35(11), pp. 1073–1082. doi.org/10.1080/02640414.2016.1210197

    5. Momma, H., Kawakami, R., Honda, T. and Sawada, S.S. (2022) Muscle-strengthening activities are associated with lower risk and mortality in major non-communicable diseases: a systematic review and meta-analysis of cohort studies. British Journal of Sports Medicine, 56(13), pp. 755–763. doi.org/10.1136/bjsports-2021-105061

    6. McCarthy, D. and Berg, A. (2021) Weight loss strategies and the risk of skeletal muscle mass loss. Nutrients, 13(7), p. 2473. doi.org/10.3390/nu13072473

Meal Timing

When you eat matters less than what and how much. But consistent patterns still help.

What The Evidence Says:

Intermittent fasting versus continuous restriction. A 2024 network meta-analysis by Huang et al.¹ and a 2025 systematic review by Semnani-Azad et al.² (99 RCTs, 6,582 adults) found that all intermittent fasting strategies and continuous energy restriction reduced body weight compared to unrestricted eating, but only alternate day fasting showed meaningful benefit over continuous restriction specifically. This strongly supports the view that energy deficit drives outcomes, not the timing pattern itself.

Front-loading calories. Young et al.³ found in a systematic review and meta-analysis that consuming more calories earlier in the day was associated with modestly better weight loss outcomes in energy-restricted contexts, potentially through improved circadian alignment.

Meal regularity. Lopez-Minguez et al.⁴ found that later meal timing was independently associated with higher BMI and worse cardiometabolic risk markers. Horikawa et al.⁵ found that regularly skipping breakfast was associated with higher prevalence of overweight and obesity. Davis et al.⁶ reviewed broader meal timing evidence, concluding irregular patterns and late eating are consistently associated with weight gain risk.

How this applies to you?

Lose Weight - Intermittent fasting supports fat loss primarily by making it easier to maintain an energy deficit, not through unique metabolic mechanisms. Front-loading calories may offer modest additional benefit for some people.

Build Muscle - For most people aiming to build muscle, total daily protein and calorie intake are likely to matter more than meal timing. A regular eating window may help manage appetite during a calorie surplus.

Track My Health - Consistent eating patterns, including not routinely skipping meals, are associated with healthier weight and metabolic outcomes. Replenish tracks eating windows to offer awareness and gentle suggestions, not rules.

    1. Huang, J. et al. (2024) Comparing caloric restriction regimens for effective weight management: a systematic review and network meta-analysis. International Journal of Behavioral Nutrition and Physical Activity, 21(1), p. 108. doi.org/10.1186/s12966-024-01657-9

    2. Semnani-Azad, Z., Khan, T.A., Chiavaroli, L. et al. (2025) Intermittent fasting strategies and their effects on body weight and other cardiometabolic risk factors: systematic review and network meta-analysis. BMJ, 389, e082007. doi.org/10.1136/bmj-2024-082007

    3. Young, I.E., Poobalan, A., Steinbeck, K., O'Connor, H.T. and Parker, H.M. (2023) Distribution of energy intake across the day and weight loss: a systematic review and meta-analysis. Obesity Reviews, 24(3), e13537. doi.org/10.1111/obr.13537

    4. Lopez-Minguez, J., Gómez-Abellán, P. and Garaulet, M. (2019) Timing of breakfast, lunch, and dinner: effects on obesity and metabolic risk. Nutrients, 11(11), p. 2624. doi.org/10.3390/nu11112624

    5. Horikawa, C. et al. (2011) Skipping breakfast and prevalence of overweight and obesity in Asian and Pacific regions: a meta-analysis. Preventive Medicine, 53(4–5), pp. 260–267. doi.org/10.1016/j.ypmed.2011.08.030

    6. Davis, R., Rogers, M. and Coates, A.M. (2022) The impact of meal timing on risk of weight gain and development of obesity. Current Diabetes Reports, 22, pp. 147–155. doi.org/10.1007/s11892-022-01457-0

Limitations of this evidence: Meal timing research is an evolving field. Many studies are short-term, use variable definitions of intermittent fasting, and involve specific population groups. We have cited the strongest available evidence but acknowledge this area carries more uncertainty than others on this page.

Guidelines & Institutional Sources

  • NICE (National Institute for Health and Clinical Excellence)

    Overweight and obesity management [NG246], 2025

    NICE NG246 is the current consolidated UK clinical guideline on overweight and obesity management in adults, replacing all previous NICE guidance on this topic. It synthesises the most up-to-date RCT and systematic review evidence on dietary, behavioural, and physical activity interventions. For exercise, it recommends that people with overweight or obesity be encouraged to engage in moderate-intensity physical activity on most days of the week, with the specific volume guided by individual capacity and the WHO 150-minute weekly target as a reference benchmark. NG246 also reinforces that no single dietary pattern is superior for long-term weight management, and cautions against prescribing specific macro ratios without regard for adherence and food quality, which is directly consistent with Replenish's approach to calorie and carbohydrate guidance.

    nice.org.uk/guidance/ng246

    Used in: Exercise (all goals) · Calories (Lose Weight)

  • WHO (World Health Organisation)

    WHO Guidelines on Physical Activity and Sedentary Behaviour, 2020, published via Bull et al., British Journal of Sports Medicine

    The WHO 2020 Physical Activity Guidelines were developed through a systematic review process covering evidence from hundreds of studies across populations globally. The guidelines recommend 150–300 minutes of moderate-intensity aerobic activity per week, or 75–150 minutes of vigorous-intensity activity, plus muscle-strengthening activities on two or more days. These figures represent dose thresholds: the evidence shows that a substantial proportion of physical activity health benefits (reduced cardiovascular disease, cancer, type 2 diabetes, and all-cause mortality) are realised when these targets are met. The guidelines explicitly acknowledge that any activity is beneficial relative to none, and that benefits increase progressively with volume. Replenish uses the WHO 150-minute moderate and 75-minute vigorous thresholds as the reference framework for its exercise guidance, with goal-specific adjustments for fat loss (aerobic emphasis) and muscle building (resistance volume, per Schoenfeld et al.) built on top of this base.

    doi.org/10.1136/bjsports-2020-102955

    Used in: Exercise (all goals)

  • SACN (Scientific Advisory Committee on Nutrition)

    Dietary Reference Values for Energy, 2012

    SACN's 2012 report is the definitive UK authority on dietary energy requirements. It used doubly-labelled water (the gold standard for measuring free-living total energy expenditure) to derive Estimated Average Requirements (EARs) for energy across all age and sex groups. The report was explicit that these EARs are population-level averages and carry significant individual variability. Specifically, SACN noted that a meaningful proportion of individuals will have energy needs substantially above or below the EAR, and that the values are not appropriate as targets for individuals without adjustment. SACN also sets out physical activity level (PAL) multipliers used to convert resting energy expenditure into total daily requirements. Replenish references SACN's EARs as the UK evidence baseline for calorie range generation across all three goals, applied via the Mifflin–St Jeor equation for individual BMR estimation and PAL-adjusted for activity level.

    gov.uk, SACN energy report

    Used in: Calories (all goals)

  • PHE (Public Health England)

    Government Dietary Recommendations, 2016

    PHE's Government Dietary Recommendations set out the UK's Reference Nutrient Intakes (RNIs) for energy and all key nutrients across all age and sex groups. These are the figures used on UK food labels and in NHS dietary guidance. For protein, the RNI is 0.75 g/kg/day for adults (rounded to 0.8 g/kg/day in standard usage), derived from the population requirement to meet the needs of 97.5% of sedentary adults. Replenish uses this as the protein baseline for the Track My Health goal, while the Lose Weight and Build Muscle goals apply higher targets grounded in exercise-specific meta-analyses (Morton et al., Longland et al.) that demonstrate the RNI is insufficient for people who are physically active. PHE's recommendations on carbohydrates (at least 50% of dietary energy from carbohydrate, with free sugars below 5%, saturated fat below 10%, and dietary fibre above 30 g/day) form the basis of Replenish's balanced macro default split. PHE guidance does not endorse low-carbohydrate or ketogenic approaches as a primary dietary strategy for the general population, which is consistent with the Cochrane and NICE evidence cited elsewhere on this page.

    gov.uk, Dietary Recommendations PDF

    Used in: Calories, Protein, Carbohydrates & Fats (all goals)