Mostly false
Your metabolism slows down after 30
A large multi-national analysis of doubly-labelled-water data found total energy expenditure, adjusted for body composition, is stable from roughly age 20 to 60, and declines only afterwards.
Metabolism claims, checked
Three verdicts rather than two, because almost none of these claims are simply false — and naming the true part is what makes the correction stick.
Partly true
Eating late at night makes you gain weight
Controlled feeding studies find later eating is associated with greater hunger, altered energy expenditure and changes in adipose gene expression, independent of total intake.
Mostly false
Breakfast kick-starts your metabolism
Randomised trials of breakfast assignment find little effect on weight, and no meaningful effect on total energy expenditure.
Partly true
Eating too little puts you in starvation mode so you stop losing
Adaptive thermogenesis is real: energy expenditure falls somewhat more than body-composition change predicts, and the Biggest Loser follow-up documented it persisting for years.
Mostly false
Green tea and similar supplements burn fat
Meta-analyses of catechin and caffeine preparations find effects on weight that are statistically detectable and clinically trivial — a fraction of a kilogram.
Mostly false
A kilogram of muscle burns hundreds of calories a day
Resting skeletal muscle uses roughly 13 kcal per kilogram per day. Adipose tissue uses about 4.5.
Partly true
Continuous glucose monitors reveal which foods are bad for you
Postprandial glucose responses genuinely vary between people for the same food. Whether acting on those readings improves outcomes in people without diabetes has not been demonstrated.
Related reading
GLP-1 Evidence
What the trials actually show about semaglutide, tirzepatide and the rest of the GLP-1 class.
Fasting Evidence
Intermittent fasting, time-restricted eating and meal timing, judged on the trial data.
Weight Loss Evidence
Diets, drugs, behaviour and maintenance — ranked by the strength of the evidence behind them.
Sleep Evidence
Sleep, circadian rhythm and the wearables that claim to measure both.