DIET

Morton, R. W., Murphy, K. T., McKellar, S. R., Schoenfeld, B. J., Henselmans, M., Helms, E., et al. (2018). British Journal of Sports Medicine, 52(6), 376-384.

Meta-analysis of 49 studies (1,863 participants) found protein supplementation significantly increased fat-free mass, strength, and muscle fiber cross-sectional area during resistance training. Meta-regression found the benefit plateaued at a total protein intake of roughly 1.6g per kg of bodyweight per day, more than that added little additional benefit on average.

Tagawa, R., Watanabe, D., Ito, K., Ueda, K., Nakayama, K., Sanbongi, C., Miyachi, M. (2021). Nutrition Reviews, 79(1), 66-75.

A larger, more recent analysis than Morton et al. 2018 above: 105 randomized controlled trials, 5,402 participants. Found the dose-response relationship between protein intake and lean mass gain extends much further than the older 1.6g/kg plateau estimate, continuing up to roughly 3.5g/kg per day. Resistance training specifically slowed the decline in returns seen above 1.3g/kg in the broader (including non-training) dataset. Doesn't overturn Morton et al.'s finding so much as add nuance: intakes meaningfully above the older plateau estimate still show real benefit, especially for people actually training.

Helms, E. R., Spence, A. J., Sousa, C., Kreiger, J., Taylor, S., Oranchuk, D. J., Dieter, B. P., Watkins, C. M. (2023). Sports Medicine - Open, 9, 102.

Randomized 21 trained lifters (17 completers) into maintenance calories, a moderate surplus (~490 kcal/day, +5%), or a large surplus (~720 kcal/day, +15%), 8 weeks of supervised full-body training. The moderate and large surplus groups gained the same total body mass, and showed no meaningful difference in actual muscle thickness, the larger surplus mainly produced more fat gain (skinfolds increased noticeably more). One wrinkle: the large-surplus group did show a bigger bench press strength gain, though squat strength showed no advantage. As the authors put it, faster rates of weight gain mostly just increase the rate fat accumulates, not the rate muscle or strength grows.

Gavanda, S., Arnet, L., Löffler, D., Dissemond, J., Havers, T., Wiewelhove, T., Geisler, S., Held, S., Brinkmann, C., Isenmann, E. (2026). The Journal of Nutrition, 156(9), 101722.

23 resistance-trained individuals randomized to a 16:8 time-restricted eating (TRE) window or unrestricted eating (control), both instructed to eat 300-500 kcal above maintenance, 12 weeks of supervised training 3x/week. The TRE group actually ate significantly less than prescribed (31.9 vs. a 37.5 kcal/kg/day target) and ate less protein (1.44 vs. 1.60 g/kg, still a solid intake) and fewer carbs than the control group did. Despite eating a smaller real surplus, TRE gained the same fat-free mass and muscle mass as control, and the same 1RM strength on both deadlift and bench press. Control gained significantly more body weight and fat mass. The honest read: TRE didn't boost muscle growth or protection, it just made it harder to overeat into the full prescribed surplus, and that smaller real surplus produced less fat gain without costing any muscle or strength, consistent with Helms et al. 2023 above (bigger surpluses mostly just add fat).

Zhang, M., Wang, S., Wutichat, S., Tanphanich, T., Li, H., Zhang, X. (2026). Frontiers in Nutrition, 13, 1879031.

Meta-analysis of 11 studies (303 participants, mostly young adults, interventions 4 weeks to 12 months) comparing intermittent fasting plus resistance training against resistance training alone, most fasting protocols were time-restricted eating. Found broadly similar training adaptations between groups overall (Hedges' g = 0.09, 95% CI -0.23 to 0.40), no clear differences in maximal strength, muscular endurance, hypertrophy-related outcomes, or explosive/high-speed performance. Authors' conclusion: current evidence doesn't show intermittent fasting clearly compromises resistance training adaptations, as long as training and nutrition are reasonably maintained within the eating window. Evidence is still limited (only 11 studies), so this is a directional finding, not a settled one.

Garthe, I., Raastad, T., Refsnes, P. E., Koivisto, A., Sundgot-Borgen, J. (2011). International Journal of Sport Nutrition and Exercise Metabolism, 21(2), 97-104.

Elite athletes lost weight at either 0.7%/week (slow) or 1.4%/week (fast) bodyweight loss. The slow group gained lean body mass (+2.1%) despite being in a deficit, while the fast group's lean mass was essentially unchanged (-0.2%), a significant difference between groups. Slower, more conservative weight loss rates better preserve (or even build) lean mass in trained athletes.

Areta, J. L., Burke, L. M., Ross, M. L., Camera, D. M., West, D. W. D., Broad, E. M., et al. (2013). The Journal of Physiology, 591(9), 2319-2331.

Compared the same total post-exercise protein dose split as 4x20g, 8x10g, or 2x40g over 12 hours of recovery. The moderate, evenly-spaced 4x20g pattern produced greater myofibrillar protein synthesis than either concentrating it into two large doses or spreading it too thin across eight small ones. How protein is distributed across the day appears to matter, not just the total.

Lahav, Y., Yavetz, R., Gepner, Y. (2026). Frontiers in Endocrinology, 16, 1725500.

Retrospective cohort of 304 adults who self-selected into resistance training (2-3x/week), aerobic exercise (150-250 min/week), or no exercise while following a roughly 500-calorie/day deficit with 1.5g/kg protein, tracked for an average of 5.1 months. Resistance training was the only group that gained fat-free mass despite the deficit (+0.8kg in men, +0.9kg in women), while both the aerobic and no-exercise groups lost lean mass, and fat loss was as good or better in the resistance-trained group too. Not a randomized trial, groups were self-selected rather than assigned, but a real-world result pointing the same direction as the controlled research: lifting, not just eating less, is what protects muscle in a deficit.