Juice cleanses, fad diets, and other types of lose-weight-quick schemes have been thoroughly proven to not work. A wealth of evidence from the past several decades shows that people who participate in “crash” diets almost always gain back the pounds they lost – often plus a little extra – because periods of sudden, extreme calorie restriction cause imbalances in hunger and satiety-regulating hormones that persist for months or years after the diet has ended. As a result of these physiological changes, post-dieters have increased appetites and need to eat more food than before their weight-loss period to feel full.

Moreover, short-term calorie slashing regimens fail to help people learn about balanced nutrition and do not deal with how one’s psychological relationship with food may be impacting their weight – it can, in fact, help trigger an eating disorder.

Now, as a further nail in the coffin of crash diets, a group of researchers from Georgetown University has shown that a good portion of the weight regained after food restriction takes the form of belly fat, aka visceral fat – a type of adipose tissue that accumulates around the abdominal organs and has been linked to diabetes, heart disease, cancer, and dementia; not to mention its undesirable appearance.    

The findings, presented at the American Physiological Society's Cardiovascular, Renal and Metabolic Diseases: Sex-Specific Implications for Physiology conference on October 2, was conducted only female rats, meaning that the data may not be directly comparable in humans. However, past investigations have shown that human and rat metabolism are highly similar.  

For the study, first author Aline de Souza and her team fed one group of rats 60 percent fewer calories and fed another group a standard amount of calories. A slash of this magnitude is on par with many human crash diets, corresponding to a 2,000 calorie per day intake being lowered to 800.

After just three days on the diet, the rats lost weight and showed decreases in blood volume, blood pressure, heart rate, and kidney function. They also displayed temporary halts in their cycling (the rat version of the menstruation). After the scientists switched their diets back to normal, the rats quickly returned to normal in all measures except body weight. Three months after the food restriction ended, the rats had more visceral fat than non-diet rats and less muscle tissue.

"Even more troubling was the finding that angiotensin II, a hormone in the body, was more potent at increasing blood pressure in the rats that were on the reduced-calorie diet," de Souza said in a statement. If these effects hold true in humans, this heightened response to angiotensin II – which circulates at elevated levels in times of stress – could mean that dieters are more susceptible to developing high blood pressure.