Tried a Diet? Your Body Will Fight Back with All Its Might

In 2009, Danny Cahill stood, beaming with happiness, on the glamorous stage of the American reality show 'The Biggest Loser'. Cahill was the big winner of the show's eighth season: in seven months, he lost no less than 115 kilograms. For the first time in his life, he was slim, flexible, athletic.

"I got my life back," he declared. "I feel like a million bucks."

Fast forward to 2016, and the picture is not so rosy. Cahill gained more than fifty kilograms in recent years, and he struggles hard not to gain more. And he's not alone. Out of 16 contestants on the show, all of whom lost significant amounts of weight, only one manages – with great efforts – to maintain the achievement.

Danny Cahill - before and after the diet on the reality show

What's the reason for this? It's not a lack of motivation. They participated in a grueling training program. They maintained a strict diet. They continue to exercise and watch what they eat. So why was the success so short-lived?

Fortunately for those contestants, answers are being provided. A group of researchers from the National Institutes of Health, a U.S. federal institution, chose the contestants of Season 8 to follow and conduct research on their diet success. The disappointing results were accompanied by amazing scientific findings that answer once and for all why diets usually fail – and why, sometimes, dieting is a really bad idea.

"The study's results were amazing – they showed us how much the body fights against weight loss," says Dr. Kevin Hall, who led the research team. "It's both scary and amazing. It really shocked me."

The problems faced by the contestants, the researchers found, stemmed primarily from changes in metabolic rate. When the program started, the contestants selected to participate were indeed extremely overweight but their metabolism functioned normally for their size. In other words, they burned calories at a rate expected of someone of their weight. However, by the end of the program, after the dramatic weight loss, their metabolism had significantly slowed and the body did not burn enough calories to maintain the new low weight.

Researchers have known for some time that anyone who deliberately loses weight – even if they are initially of normal weight or even underweight – will have a slower metabolism at the end of the diet. So the fact that the contestants' metabolism was slower at the end of the show was not surprising in itself. What stunned the researchers was the discovery that the metabolism did not return to normal even after six years. Worse still: as the years went by and contestants regained weight, their metabolism became even slower. The body, it seems, doubled its efforts to push the participants back to their original weight.

Danny Cahill, the big winner, was the one whose metabolism was harmed the most. After regaining fifty kilograms of what he lost, his metabolism became so slow that just to avoid gaining more weight he had to eat 800 calories less than what someone of his weight could normally afford. Any caloric deviation immediately turned into fat.

(Photo: shutterstock)

The difficulties documented in the study of the American 'The Biggest Loser' contestants help explain why it is so hard to combat the global obesity epidemic. Even the most disciplined diet enthusiasts, those willing to drastically cut their calorie intake and spend hours in the gym, struggle to maintain their weight loss over time. It's not a moral or psychological failure – but a biological mechanism that resists weight loss. Even six years after losing weight, the body will fight to return you to your original weight.

The study's findings, published today in a U.S. medical journal on obesity issues, are part of an effort to tackle the obesity epidemic and its dangers from a new angle. The fate of Cahill and his companions adds more evidence to the need to treat obesity as a chronic disease and find new ways to treat extreme overweight.

Gaining Weight – and Still Hungry

Almost anyone who has ever tried to lose weight knows the frustrating feeling: the diet may succeed, but a few months later the weight comes back – sometimes with added interest. The guilt in these cases is not entirely justified. As the study proved, those who lose weight are fighting not only a craving for food. They also need to fight their body's biological mechanisms. Whether you've lost ten kilograms or a hundred, the body will strive to return you to the previous weight. The reason? Every person has a certain weight that the body maintains easily, and fluctuations in it occur mainly with age. This weight the body fights to maintain. This is the reason for the severe slowdown in metabolism for those who have dieted.

The slowdown in metabolism is not the only weapon the body turns against you. Another problem is the complete disruption of the hunger and satiety mechanism following diets. Take for example the hormone leptin, a hormone that controls the feeling of hunger. With weight loss, leptin levels plummet and people feel hungry all the time. The result? They eat more and gain the lost weight back. The contestants who participated in the study indeed reported constant hunger. Indeed, tests conducted on them revealed very low levels of leptin. At the beginning of the program, the competitors' leptin levels were normal, but by the finale, hardly any leptin was secreted by their bodies. When they regained weight, leptin levels increased – but only to half of what they were before the diet. In other words, they gained weight – and were still very hungry.

Leptin, by the way, is just one of a group of hormones that control hunger and satiety mechanisms. Dr. Hall's group only studied it, but other studies that have looked at people who have gone on extreme diets have found that other hormones behave accordingly: hormones signaling satiety plummet, hormones reporting hunger and appetite – rise.

(Photo: shutterstock)

"I Stopped Blaming Myself"

So is there no hope for those who want to lose weight? Not exactly, the researchers say. Different people respond differently to different forms of nutrition - low-carb nutrition versus low-calorie nutrition, for instance – as well as to exercise and medications meant to assist with weight loss. And bariatric surgeries undoubtedly demonstrate much greater success in maintaining a normal weight in the long term.

But the simplistic thinking that consuming fewer calories is the answer has been unequivocally proven to be overly simplistic. "There is no doubt there are exceptional people who can ignore biological signals and maintain the new weight long-term by limiting calorie intake," says one of the researchers. "But for most people, the combination of constant hunger and a slowdown in metabolism is a recipe for weight gain – and that is why only a few diets succeed for more than a few months."

For the contestants of Season 8 of the American 'The Biggest Loser', the study's findings brought some relief. Despite the frustration over their expanding waistline, at least they now know that a lack of willpower is not the culprit. Something in their bodies, indeed, does not function as it should and makes it difficult to maintain a normal weight. "I stopped blaming myself once I got the report from Dr. Hall detailing how much my metabolism had slowed," says the winner, Danny Cahill. "At least I've been freed from the shame."