The Claim

Alternate-day fasting without net energy restriction does not significantly reduce body mass or fat mass in lean adults over a 3-week period.

Source: A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
60score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Description
1 study reviewed
In plain English

In lean adults, fasting every other day without eating fewer calories overall does not lead to a reduction in body weight or fat mass after three weeks.

See the scientific wording

Alternate-day fasting without net energy restriction does not significantly reduce body mass or fat mass in lean adults over a 3-week period, indicating that fasting alone, without calorie reduction, is ineffective for fat loss.

Why this might work

When meals are skipped on fasting days, the body responds by increasing hunger and food intake on eating days, so total calorie intake stays the same. Because no extra calories are burned or stored as fat, body mass and fat mass do not change.

Verified mechanismbased on 1 study

What the research says

1 study
  1. Study: A randomized controlled trial to isolate the effects of fasting and energy restriction on weight loss and metabolic health in lean adults

    When people skipped meals every other day but ate even more on the days they did eat (so they didn’t cut total calories), they didn’t lose any fat. This shows that just skipping meals doesn’t help you lose fat unless you eat fewer calories overall.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

Fit Body Science verdict — we translate health claims into clear verdicts backed by peer-reviewed research.

Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.