Is exercising in the morning or in the evening better?
For fat reduction and improved blood lipids, morning training has the strongest evidence. For cardiovascular health, exercising in the afternoon or evening is also perfectly fine, but avoid high doses of caffeine close to bedtime.
It depends on your goal. Want to lose fat or improve your blood lipids? Then morning training (between 6 and 8 a.m.) is the stronger choice. A 12-week study of 58 sedentary men showed that the morning group lost more fat after just four weeks. Only in that group did cholesterol and triglycerides also fall. An added benefit: evening exercisers consumed an average of 152 kilocalories extra after their workout, without feeling any hungrier. This unconsciously works against fat-loss goals.1
For cardiovascular health, the timing matters less. In that same study, evening exercise actually offered advantages: better blood flow, greater dilation of the carotid artery, and a stronger reduction in blood pressure. A large study following 92,139 people for over seven years showed that exercise at any time of day was associated with lower mortality risk. Afternoon and late-afternoon exercise (11 a.m. to 5 p.m.) was slightly more favourable than morning exercise for all-cause and cardiovascular mortality. This is an observational association, not proof of cause and effect.2
The timing also affects your sleep. Morning exercise shifts your sleep time earlier and advances the release of the sleep hormone melatonin. Evening exercisers who take caffeine as a pre-workout face additional risk: a high dose of 400 mg (equivalent to four cups of coffee) within twelve hours of bedtime substantially disrupts sleep. A normal dose of 100 mg had no measurable effect.3,4
Your own biological rhythm also plays a role. People with an evening chronotype (naturally a night owl) more often have excess weight and poorer metabolic values, partly due to eating later and less healthy eating behaviour. Whether evening types genuinely perform better with evening exercise is still unclear: the studies on this are too small for firm conclusions. In elite boxers, muscle damage and inflammation after morning sessions were lower than after evening sessions, but this says little about recreational exercisers.5 What always matters: exercising regularly is more important than finding the perfect time.
The claims are based on one small randomised study (n=58, sedentary men, PMID 40419564), one large observational cohort study (n=92,139, UK Biobank, PMID 36805455), two smaller observational studies (n=16 and n=23, PMID 36539157 and PMID 39377163), one study in elite boxers (n=21, PMID 41001950), one study in cyclists (n=10, PMID 40259503), and two review studies (PMID 36041181 and PMID 36833520). The randomised studies are small; the cohort study is large but cannot establish cause and effect. Results cannot always be generalised to all ages, sexes, and fitness levels.