Anyone who has ever tried to lose weight knows that lost pounds often find their way back home. Most dieters blame themselves for lack of discipline or failure of willpower. But an Australian physician has found that hunger associated with dieting may trigger defense mechanisms in the form of hormones that promote weight gain.
Most diets inevitably fail
People have been getting results at Joesph Proietto’s weight loss clinic in Melbourne, Australia for 15 years. But inevitably, the weight they lost gradually returns. Within a few months or years, their investment in Proietto’s clinic has gone for naught. Proietto wanted to find out why his patients, who are very motivated to lose weight, almost without exception can’t maintain long term results.
Investigating hunger hormones
Proietto’s team chose to investigate various hormones that control hunger. Previous studies had shown that during weight loss, the body produces higher levels of ghrelin, the hormone that stimulates hunger. At the same time, levels of leptin, the hormone that induces satiety, fall. Overall, there are at least nine different hormones in the blood that influence hunger. Ghrelin is the only one that stimulates appetite. The others, including insulin and amylin, work to suppress it.
Proietto’s team recruited 50 obese men and women for the study. Some dropped out, but most of them followed an extreme low-calorie diet of 500 to 550 calories a day for eight weeks. After ten weeks, participants lost an average of 30 pounds. Moving forward, participants stopped dieting and worked with nutritionists who counseled them to eat more vegetables and less fat in combination with exercise. After a year, they had gained back an average of 11 pounds and reported feeling more hungry and obsessed with food than before they lost all the weight.
A biologically altered state
Before the dieting period, immediately afterward and then a year later, Proietto drew blood from participants to measure blood hormone levels before breakfast and then every 30 minutes the following four hours after breakfast. His findings confirmed that weight loss resulted in increased levels of ghrelin and decreased levels of leptin. But he also discovered something new: all the other appetite suppressing hormones remained low.
A full year after significant weight loss, participants were stuck in a biologically altered state. Their bodies still behaved as if they were starving and were fighting to regain the lost weight. In an article about his study published in the New England Journal of Medicine, Proietto said “What we see here is a coordinated defense mechanism with multiple components all directed toward making us put on weight. This, I think, explains the high failure rate in obesity treatment.”
Challenging conventional wisdom
Prioetto’s research challenges conventional wisdom about obesity, weight loss and willpower. For years, overweight and obese people have simply been told to eat less and exercise more. While this approach brings short term results, it fails long term because the human body fights against weight loss long after the diet is over.
Years of obesity may lock in a hormone profile that works against a dieter’s best intentions. Losing weight is relatively easy. But once most people become obese, they could be doomed to return to obesity unless conventional wisdom about treatment changes.
Source: New York Times, Melbournelapband.com, New England Journal of Medicine