Fat loss is primarily determined by total energy deficit rather than the specific method used to create that deficit, and moderate calorie restriction (500-750 kcal/day below maintenance) produces sustainable weight loss of approximately 0.5-1 kg per week.

In plain English

Eat about 500 calories a day under what you burn and you will lose roughly half a kilo a week. Whether you get there by eating less, moving more, or both barely changes the result.

Why it works

When energy intake falls below expenditure, the body mobilizes stored energy (primarily adipose tissue) to cover the gap. The thermodynamic relationship between deficit and tissue loss is consistent across methods.

The evidence

• Redman, L.M., Smith, S.R., Burton, J.H. et al. (2022). Impact of Calorie Restriction on Energy Metabolism in Humans. Experimental Gerontology.

• Finkler, E., Heymsfield, S.B., St-Onge, M.P. (2012). Rate of Weight Loss Can Be Predicted by Patient Characteristics and Intervention Strategies. Journal of the Academy of Nutrition and Dietetics.

• Redman, L.M., Heilbronn, L.K., Martin, C.K. et al. (2007). Fat Loss Depends on Energy Deficit Only, Independently of the Method for Weight Loss. Annals of Internal Medicine.

Why we call confidence high

Redman et al. 2007 directly demonstrated equivalent fat loss from calorie restriction alone vs. calorie restriction plus exercise at matched deficits. The energy balance principle is one of the most replicated findings in nutrition research.

Where it applies

Healthy adults