INTERMITTENT FASTING AFTER 50: WEIGHT, MUSCLE AND WHAT THE TRIALS FOUND

Intermittent fasting after 50 helps with weight loss about as well as ordinary calorie cutting, and pooled trials found it didn't hurt most measures of strength and fitness when people kept training. The main concern at this age is muscle: in several analyses, people also lost some lean mass along with fat, and the evidence in adults over 45 is too short-term to say much about keeping muscle long term.

Weight Loss: About the Same as Eating Less

• The TREAT trial. Lowe and colleagues (2020) randomized 116 adults aged 18 to 64 with overweight or obesity to eat only between noon and 8 p.m. (16:8) or to eat three structured meals a day, for 12 weeks. The time-restricted group lost slightly more weight, but the difference between groups wasn't significant. In the in-person subgroup, the time-restricted group lost more appendicular lean mass, the muscle in the arms and legs. The authors concluded time-restricted eating alone was not more effective than eating throughout the day. Two authors disclosed ties to a company selling metabolic-tracking products.
• Adults 45 and older. A 2026 scoping review (Santero) of 20 randomized trials in adults 45 and older found fat and weight losses with intermittent fasting similar to those with continuous calorie restriction, and generally small differences in fat-free mass over trials that mostly lasted 12 weeks or less. The authors said the evidence doesn't allow firm conclusions about preserving fat-free mass long term in older people.
• By age group. A 2026 meta-analysis (Xing) of 28 trials split participants by age. In adults 45 and older, fasting went with improvements in triglycerides, blood pressure and insulin sensitivity, but also a loss of fat-free mass and, in a sensitivity analysis, a rise in LDL cholesterol. The authors rated the certainty low to very low and called the age patterns hypothesis-generating.

Does It Cost You Strength or Fitness?

Kazeminasab and colleagues (2025) pooled 35 randomized trials of 1,266 adults aged 18 to 65 that compared intermittent fasting or calorie restriction plus exercise with exercise alone. Adding the diet didn't significantly change VO2 max, bench press, leg press, knee strength, jumping or gait speed, and grip strength was slightly higher. It did reduce weight and fat, and it also reduced fat-free mass by about 1.7 kg.

Exercise also helps the diet. In 12 trials of adults averaging 40 with overweight or obesity (Dai 2025), fasting plus exercise lowered fat mass, waist size, insulin and LDL more than fasting alone, and improved cardiorespiratory fitness.

Longer Fasts and Hard Training

Daily 16:8 eating isn't the same as a month of dawn-to-dusk fasting. An overview of 14 systematic reviews on Ramadan fasting in athletes (Trabelsi 2024) found it was associated with shorter, poorer sleep, more fatigue, and worse results on high-intensity exercise tests, while lean mass was preserved. The underlying reviews were low to critically low in quality.