Objective The prevalence of overweight and obesity is increasing in most countries, including Germany. The idea of estimating the population-wide energy gap that is likely responsible for the epidemic has recently been introduced and discussed.Design Using published estimates of body weight from population-based data of national health surveys (1985-2002), the energy gap was calculated by estimating the distribution of the rate of weight gain within the German population (25-69 years of age) and the amount of excess energy storage that is responsible for this population-wide pattern of weight gain.Setting Germany.Subjects A representative sample of 26 614 participants (12 984 men, 13 630 women).Results The average annual weight gain was 022 kg for men and 0.32 kg for women over the 17-year period. An estimated 90 % of the population gained < 054 kg/year. Assuming that each kilogram of weight gained represents 32238 kJ (7700 kcal), the estimated energy accumulation was 19 kJ (464 kcal)/d in men and 28 kJ (675 kcal)/d in women aged 25-69 years. The distribution of estimated energy accumulation for 90 % of the German population was < 50 kJ (12 kcal)/d.Conclusions With an assumed energy efficiency of 50 %, the findings suggest that weight gain could be prevented in 90 % of the German population with < 100 kJ (24 kcal) reduction in energy intake or increase in energy expenditure per day. Theoretically, further weight gain might be prevented using a small-changes approach that emphasizes the importance of making small changes in physical activity and food intake. © 2010 The Authors.