Exercise and Weight Loss: Does It Work?

Chapter summary

Author’s position: Exercise for weight loss is close to useless. If that is your reason, change diet first, then exercise for health.
Exercise does not reduce weight long term. It is unclear whether exercise makes people hungrier or whether they eat more to compensate.
Weight loss gives most of the health benefit and makes exercise easier for overweight people.

The author’s case: You can eat hundreds of calories in a few seconds, and burning them takes much longer. A 70kg person burns about 560 calories an hour at 8kph. In a 1996 twin study with a 650-calorie daily deficit, eight pairs lost anywhere from nothing to 8kg over three months, so genes shape the response (Bouchard).
The health bodies’ case: Susan Anderson of the Heart Foundation calls it irresponsible to say exercise is useless for weight loss, because movement is fundamental to health. Julie Gilbert of the Dietitians Association of Australia says weight loss is a combination, with roughly 70% from portion cuts and 30% from exercise.
Common ground: Both agree exercise is needed for health. They differ on how much it helps the scales.

Physical inactivity accounts for about 6% of global deaths (WHO).
Vissers (2013) found moderate to vigorous aerobic exercise reduces visceral fat without diet change. Weight training did little for visceral fat.
Walking increases the size of the hippocampus and may delay dementia onset by two years.
Muscle and mitochondria raise basal metabolism, and exercise reduces fat inside cells.
Mental health: It improves mood, sleep and self-esteem, cuts anxiety and stress response, and can work as well as therapy or medication for depression, especially over the long term. Brisk walking and cycling work best.

Even a healthy amount of exercise cannot offset long sitting.
Cutting sitting to under three hours a day could add two years to US life expectancy, and less than two hours of TV adds 1.4 years (BMJ Open 2012).
In a survey of 6,379 people, women who cut sitting from a full workday to three hours cut kidney disease risk by more than 30%, and men by 15%.
Sitting is linked to metabolic syndrome, colorectal cancer survival and mental health.

Move slowly most of the time and avoid sitting for more than 30 minutes.
Move fast occasionally.
Keep moving as you age. Someone who stops walking 500m a day is at high risk within months.
Do not change your exercise routine during the first 12 weeks of the take-out plan.

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World Health Organization (2009) Global Health Risks. WHO Press.
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Bharakhada, N. et al. (2012) Association of sitting time and physical activity with CKD. Nephrol Dial Transplant.
Edwardson, C. et al. (2012) Association of sedentary behaviour with metabolic syndrome: a meta-analysis. PLoS ONE 7(4):e34916.
Campbell, P. et al. (2013) Associations of recreational physical activity and leisure time spent sitting with colorectal cancer survival. J Clin Oncol.
George, E. et al. (2013) Chronic disease and sitting time in middle-aged Australian males. Int J Behav Nutr Phys Act.