Yo-yo effect
The yo-yo effect is regaining weight after a diet, sometimes beyond your starting weight – it's your body fighting back, not a lack of discipline.
Ausführlich erklärt
The yo-yo effect describes the ups and downs of weight after dieting: quickly down, slowly back up – sometimes beyond the starting weight. It isn't a sign of weakness, but a perfectly normal response of the body to scarcity. Very strict crash diets make it particularly hard: they're almost impossible to sustain, and afterwards old eating habits meet a body that burns less.
Three mechanisms work hand in hand. First, in a large calorie deficit, energy expenditure drops by more than the lower body weight can explain – researchers call this adaptive thermogenesis. Second, with a large deficit, little protein and no strength training, the body breaks down muscle as well as fat – and less muscle means slightly lower energy use and less strength for being active. Third, the hunger hormone ghrelin rises while satiety hormones fall; in one study, this was still measurable a year after the diet. A small, well-known study of 14 contestants from the US show “The Biggest Loser” (Fothergill 2016) found that six years after their extreme weight loss, their resting metabolic rate was on average around 500 kcal below the expected value – even though most of them had regained weight.
The counter-strategy is slow and boring, but it has the best chance of success: a moderate deficit of 300 to 500 kcal a day, which initially leads to a loss of around 0.3 to 0.5 kilograms a week. Enough protein (the German Nutrition Society (DGE) recommends 0.8 grams per kilogram of body weight a day for adults, and 1.0 gram from the age of 65; experts often advise a little more when losing weight) and strength training protect your muscles. And above all: no diet with an end date, but habits you'll still enjoy in five years' time.
If you've already been through several rounds of yo-yo dieting, that's no reason to blame yourself – you simply used methods that don't work long term for the vast majority of people. For children and teenagers, going on a diet on their own is off-limits: they're still growing, and often the goal is to grow into their weight rather than lose it. What's right in an individual case is best discussed with your paediatrician.