It’s not really news that obesity and the trend of increasing waistlines seems to only be heading upward—and outward. Despite efforts to fight the fat, many people end up regaining the weight they lose when they diet in a phenomenon known as “weight cycling” or “yo-yo dieting.”
Weight cycling can be frustrating, and some experts say that a continual cycle of gaining and losing large amounts of weight could be associated with health risks such as high blood pressure. Drastic periods of weight loss and gain may also slow down your metabolism and eventually lead to increased weight and fat mass.
Three main hormones regulate body weight:
- Leptin signals that we’re full. When we lose weight, leptin levels drop as if to tell us, “Hey, eat more!”
- Ghrelin is sometimes called the “hunger hormone.” Ghrelin levels increase during weight loss and stimulate our appetite.
- Insulin is a storage hormone. When insulin levels are high, it’s telling our body to store the food we’ve just eaten. When levels are low, insulin tells our body to break down stored fat to use for energy.
Together, these three hormones relay signals that tell us when, how much and what to do with what we eat. Understanding how they change in response to weight cycling may help researchers better understand why people struggle to keep weight off. And, surprisingly, yo-yo dieting could even have some beneficial effects over time.
A recent study published in the American Journal of Physiology—Endocrinology and Metabolism explored how yo-yo dieting influences how the body adapts to repeated weight loss. Researchers studied rats that went through four cycles of weight cycling in a year. Once they lost the weight, they were allowed to eat as much as they wanted until they gained the weight back. The rats that yo-yoed in weight throughout the year were compared to another group that ate whatever and whenever they pleased.
While the weight cycling rats regained more weight during each cycle, at the end of the year they actually weighed less and had less body fat than the group that ate freely. The slimmer mice also had better blood sugar control, which is an important marker of metabolic health. Interestingly, while leptin, ghrelin and insulin levels fluctuated throughout the study period, once the rats had regained weight for the last time, their hormone levels and metabolism were no different—no better or worse—than at the start of the trial.
These results suggest that yo-yo dieting may not be a bad thing, at least in rodents. It’s an interesting way to look at how different cycles of feasting and fasting could affect human health. While you may think there is no use in dieting if you’re just going to gain the weight back anyway, it appears that weight cycling could have some long-term benefits. It may be better than trying nothing at all.
Brady Holmer is a PhD student in exercise physiology at the University of Florida. His lab focuses on cardiovascular physiology; mainly how exercise can play a role in health, disease and aging.