&gt;&gt; In a 2016 study published in the journal Obesity, researchers followed 14 contestants during and after one season of the show. Contestants experienced drastic weight loss, losing an average of more than a hundred pounds each. By the final weigh-in, contestants' leptin levels had plummeted, so that they had very little of the hormone, rendering them constantly hungry. They also had a slow metabolism. In other words, their thyroid function—which governs metabolism and many other bodily functions—had slowed.

&gt;&gt; **Over the following six years, the combined effects of these hormonal changes conspired to make the contestants regain much, if not all, of the weight they'd lost. But the truly shocking part was that their leptin and metabolism levels never rebounded to what they had been before the show. In fact, the more weight a contestant lost, the worse his or her slow metabolism became. This explains why weight regain was inevitable, even though they were eating less food than ever.**

&gt;&gt; [...]

&gt;&gt; However, "The Biggest Loser" also suggests that for those who have severe obesity, the most effective path to drastic weight loss that is sustained may not be diet and exercise, even though those are key elements of a healthy lifestyle and important for maintaining weight loss.

&gt;&gt; [...]

&gt;&gt; **Whether you're trying to lose 10 pounds or 50, slow and steady is far more effective. Because gradual weight loss doesn't cause the extreme changes in hunger hormones and the slow metabolism seen with the "Biggest Loser" contestants,** you're less likely to regain weight with the slower route.

Source: [Harvard Health Publishing -  Lessons from “The Biggest Loser”](https://www.health.harvard.edu/diet-and-weight-loss/lessons-from-the-biggest-loser)