In people trying to lose weight, there are often repeated cycles of weight loss and regain. Weight cycling is, however, not limited to obese adults but affects people of normal weight, particularly young women, who are unhappy with their appearance. Furthermore, the onset of a pattern of weight cycling is shifting towards younger ages, owing to the increasing prevalence of overweight and obesity in children and adolescents, and the pressure from the media and society for a slim image even for normal weight children. Although there is still controversy whether weight cycling promotes body fat accumulation and obesity, there is mounting evidence from large population studies for increased cardiovascular risks in response to a behavior of weight cycling. Potential mechanisms by which weight cycling contributes to cardiovascular morbidity include hypertension, visceral fat accumulation, changes in adipose tissue fatty acid composition, insulin resistance and dyslipidemia. Moreover, fluctuations in blood pressure, heart rate, sympathetic activity, glomerular filtration rate, blood glucose and lipids that may occur during weight cycling--with overshoots above normal values during weight regain periods--put an additional load on the cardiovascular system, and may be easily overlooked if humans or animals are studied during a state of relatively stable weight. Overshoot of those risks factors, when repeated over time, will stress the cardiovascular system and probably contribute to the overall cardiovascular morbidity of weight cycling.