A cura di @S1m0n4.

Le diete ipocaloriche non garantiscono che il peso di fine dieta venga mantenuto nel tempo, soprattutto se si ritorna alle abitudini alimentari che hanno preceduto la dieta.

Questo articolo apparso su The Conversation ci spiega quali sono i meccanismi che contribuiscono all’effetto yoyo:

• la leptina, un ormone che aumenta la sensazione di fame fino a un anno dopo la dieta
• il metabolismo rallentato
• l’impatto sul palato

Although cutting calories can cause weight loss, it does not follow that if a person returns to their usual diet they will maintain their new low weight. In fact, studies have found that after a low calorie diet, between one and two-thirds of people regain more weight than they had lost initially.

The fundamental problem with cutting calories is that the human body defends its original weight. Evolution has produced a body that anticipates future famine, with the result that when you reduce calorie intake there are strong physiological pressures to replace the lost energy.

For example, dieting causes the gut to release a range of hormones that increase appetite: changes that are still apparent after the diet is over. Leptin – which makes one feel satisfied and full – has been found to be still reduced a year after dieting has finished, while ghrelin, a hormone which stimulates appetite, remains raised. So even a year after a person finishes their diet, they will feel hungrier than when they started dieting, and still anticipate a higher food consumption than before the diet.

Reducing food intake also reduces the body’s metabolic rate and production of body heat. The resulting lower energy consumption helps a more thrifty body to return to its initial weight, as fewer calories are needed to fulfil these basic bodily functions.