Running for Weight Loss
Running burns more energy per minute than almost any common exercise, but trials of running or aerobic training without dietary change produce only about two kilograms of weight loss over several months, because appetite and daily activity compensate.
Plain English
Patient-Friendly Explanation
Running is the most time-efficient way most people have to burn energy. The energy cost of running is roughly one kilocalorie for every kilogram of body weight for every kilometre, so a 70 kilogram adult running five kilometres uses around 350 kilocalories, and running costs about twice as much per minute as brisk walking. That arithmetic makes weight loss look easy, and it is not, because the arithmetic leaves out the body. Studies of running and other aerobic training given on their own, without a diet, produce much less weight loss than the energy ledger predicts. In a trial of 234 overweight and obese adults randomised to eight months of aerobic training, resistance training or both, the aerobic group lost about 1.8 kilograms and the combined group about 2.4 kilograms, while the resistance-only group barely changed on the scale though it gained muscle. In a year-long trial of postmenopausal women, exercise alone produced about 2.4 per cent of body weight, diet alone about 8.5 per cent, and diet with exercise about 10.8 per cent. The gap between the arithmetic and the results comes from compensation: appetite rises, and people move less during the rest of the day, together erasing perhaps a third to a half of the deficit running creates. None of that makes running useless. It is the most efficient way to improve fitness, running is strongly associated with better long-term weight maintenance, and comparing large cohorts of runners and walkers at matched energy expenditure shows similar health benefits, which means the best choice is the one you will keep doing. Two practical warnings. Beginners get injured, at a rate of roughly 18 injuries per thousand hours of running, so start with walking and short running intervals rather than a fast five kilometres. And if the knees, hips or back are already painful, or the body mass index is high, swimming and cycling carry the same heart and lung benefit with a fraction of the joint load.
Medical
Clinical Definition
Running has a high energy cost per unit of time, quantified in the Compendium of Physical Activities as approximately 9 metabolic equivalents at 8 kilometres per hour, 10 at 10 kilometres per hour and 12 at 12 kilometres per hour, with an approximate cost of one kilocalorie per kilogram per kilometre. Per unit of distance the difference from walking is real but smaller than commonly assumed: in indirect calorimetry of 24 adults, running 1,600 metres cost 481 kilojoules against 340 kilojoules for walking the same distance on a treadmill, and 480 against 334 kilojoules on a track, a difference of about 40 per cent. The randomised evidence for training alone is consistent and modest. In the STRRIDE AT/RT trial, 234 overweight or obese adults completed eight months of aerobic training, resistance training or both, with body mass reductions of approximately 1.8 kilograms for aerobic training, 2.4 kilograms for combined training and no significant change for resistance training alone, the last accompanied by an increase in lean mass. In the Nutrition and Exercise for Women trial of 439 postmenopausal women over 12 months, exercise alone produced a 2.4 per cent reduction in body weight, diet alone 8.5 per cent and diet with exercise 10.8 per cent. Observational data are more favourable for sustained weight control: higher volumes of running are associated with less weight gain across decades, and in the National Runners and Walkers Health Studies, matched for energy expenditure, the two activities produced comparable risk reductions for hypertension, dyslipidaemia and diabetes. The discrepancy between predicted and observed weight loss is attributed to compensatory increases in energy intake and reductions in non-exercise activity thermogenesis, which together offset an estimated 30 to 50 per cent of the exercise-induced deficit. Prescription should therefore favour volume, frequency and adherence over intensity, and should account for injury risk: prospective data place the incidence of running-related injury in novice runners at approximately 17.8 per 1,000 hours, rising with weekly distance gains and previous injury, while cycling and swimming deliver comparable cardiorespiratory benefit at much lower joint loading for patients with osteoarthritis or a high body mass index.
Key Insight
Why It Matters
Running is the most efficient way to buy fitness, not the easiest way to lose weight, and the compensation that erases a third to a half of its energy cost is why it works best alongside a dietary plan rather than instead of one.
Sources
Reviewed against standard medical references.
Medically reviewed by
Family Physician & Registered Acupuncturist, Accord Medical Clinic. MBBS (NUS), Graduate Diploma in Family Medicine (NUS), Graduate Diploma in Acupuncture (Singapore College of TCM).
Last reviewed: October 2026
This page is general health education, not medical advice. Whether any treatment is appropriate for you is a decision made in consultation after assessment.
