People who go without food for 18 hours or more overnight tend to gain less weight each year than those who eat again sooner after dinner — and those who snack late at night tend to gain a little more.
Scientific Claim
In a cohort of 50,660 North American adults aged 30 and older, an overnight fast of 18 hours or longer is associated with a small annual reduction in body mass index (BMI) of -0.02 kg/m²/year compared to a 12–17 hour fast, while a fast shorter than 12 hours is associated with a small annual BMI increase of +0.02 kg/m²/year.
Original Statement
“Correspondingly, the BMI of subjects who had a long overnight fast (≥18 h) decreased compared with those who had a medium overnight fast (12–17 h) (P < 0.001). ... subjects with a short overnight fast (prevalence: 14.2%) whose BMI was relatively increased (0.02; 95% CI: 0.01, 0.03), both compared with a medium overnight fast (prevalence: 77.7%) of 12–17 h (P-trend <0.001).”
Evidence Quality Assessment
Claim Status
overstated
Study Design Support
Design supports claim
Appropriate Language Strength
association
Can only show association/correlation
Assessment Explanation
The study reports associations between fasting duration and BMI change but cannot prove fasting causes weight changes. The original text uses 'decreased' and 'increased' as if causal; only association is valid.
Evidence from Studies
Supporting (1)
People who go 18+ hours without eating at night lost a tiny bit of weight each year, while those who ate more often (especially snacks) gained a tiny bit — just like the claim says.