Intermittent fasting and fat-free mass in middle-aged and older adults: a scoping review
This scoping review of 20 randomized trials in adults aged 45 and older found generally small between-group differences in total fat-free mass over commonly 12 weeks or less; the evidence does not allow definitive conclusions about long-term fat-free mass preservation. [1]
Automatic summary · not editorially reviewed
The key findings
The review compared intermittent fasting with a habitual diet or continuous energy restriction for fat-free mass in adults aged 45 and older. [1]
Twenty randomized controlled trials with 1653 participants, 64% female, were included, mostly adults with overweight or obesity. [1]
Most studies measured total fat-free mass or lean mass, which may not reflect skeletal muscle changes, and the evidence does not permit definitive conclusions. [1]
The source at a glance
- Study type / format
- Scoping review of randomized controlled trials (abstract)
- Population / context
- Middle-aged and older adults aged 45 and older, mostly with overweight or obesity
- Summary based on
- Study abstract
- Original publication
- July 2, 2026
Fasting versus habitual diet or energy restriction in adults 45+
The review asked how intermittent fasting affects fat-free mass in middle-aged and older adults compared with a habitual diet or continuous energy restriction. It also looked at other body measurements, functional performance and quality of life. Because muscle mass naturally declines with age, the authors noted concerns about fat-free mass in aging populations.
Supporting source [1]
Twenty randomized trials, mostly overweight or obesity, mostly 12 weeks or less
Twenty randomized controlled trials with 1653 participants, 64% female, were included; most participants had overweight or obesity. Interventions commonly lasted 12 weeks or less. Between-group differences in total fat-free mass were generally small. Intermittent fasting reduced fat mass, body weight and waist circumference comparably to continuous energy restriction, and body weight and fat mass reductions were more consistently reported versus a habitual diet. Alternate-day fasting and alternate-day modified fasting were commonly studied and often linked to body weight and fat mass reductions, particularly versus a habitual diet.
Supporting source [1]
Total fat-free mass measured, not skeletal muscle; long-term evidence lacking
Most studies measured total fat-free mass or lean mass with dual-energy X-ray absorptiometry or bioelectrical impedance analysis, which may not reflect skeletal muscle changes. Evidence on insulin-related outcomes, dietary protein intake and combined fasting plus physical activity was limited and heterogeneous. Functional and quality-of-life outcomes were rarely assessed. The authors conclude that the evidence does not permit definitive conclusions about fat-free mass preservation, especially long-term, and call for longer, standardized trials.
Supporting source [1]
How to interpret this
Abstract only; the full text was not reviewed. Durations were commonly 12 weeks or less, so long-term effects are unknown. Most measures were total fat-free mass or lean mass, not skeletal muscle. Functional and quality-of-life outcomes were rarely assessed, and evidence on insulin-related outcomes, protein intake and combined exercise was limited and heterogeneous.
Based on the study abstract; the full paper, tables and supplementary data were not reviewed.
Source & supporting passages
Santero S, Blagojević BD, Merzah M, Celada Guerrero JA, Cena H, Ordovas JM, Ruiz LD. · europepmc.org · July 2, 2026