Initial studies linked weight cycling to health risks and disease, and this information is frequently cited on television shows and in magazines. However, there is a study error that indicates these health risks may be overstated, as studies did not screen out individuals who came into the study with risk factors, such as weight loss due to illness. At least some of the reported health risks of weight cycling are due to the inclusion of this group.
Another concern, that weight cycling changes metabolism and reduces a dieter's ability to lose weight, was studied by a large group of doctors from various institutions in the US and Canada. This study, involving over 400 women, found that weight cycling does not negatively affect future weight loss. These women were put on various regimens of diet and exercise. Women who had a history of regular weight cycling were just as able as other women to take part in diet and exercise programs and showed no difference in physiological measures of factors thought to increase weight gain and metabolic rate, such as insulin, blood pressure, and hormones. (Differences between women did appear, but could be accounted for by a higher or lower BMI. Weight cycling did not appear to be a factor.)
The take-away from this study? It may be that taking two steps forward and one step back in both healthier diet and improved exercise, may be a legitimate way to reduce your BMI and improve your overall health.