The scale sometimes shows a lighter number after a sweltering day. Enough to nourish the hope of losing a few kilos thanks to the heatwave. But is this phenomenon really synonymous with weight loss? While almost all of mainland France is affected by extreme heat, many French people are wondering about the effects of the heatwave on weight. Questioned on the subject, Dr. Gérald Kierzek, emergency physician and medical director of True Medical, provides nuanced explanations.
Why the heatwave sometimes lowers the number on the scale
The specialist immediately confirms that “we lose weight during heat waves“, before adding: “but in a very limited and often misleading way.“
When temperatures rise, the body implements several mechanisms to maintain a stable temperature, including sweating. After a day spent under more than 30°C, it is not uncommon to notice a temporary reduction in weight.
“By sweating, the body eliminates water and minerals, which can lower the weight on the scale.“
This loss is essentially water and disappears quickly as soon as you drink enough to compensate for the losses linked to sweat.
In other words, seeing one kilo less on the scale after an episode of extreme heat does not mean that the body has drawn on its fat reserves.
Less appetite during hot weather, a real but limited effect
Heat also modifies eating behavior. Large meals often become less appealing and many favor fresher, lighter foods.
Dr. Gérald Kierzek observes that “in high heat, some people are less hungry: the body spends less energy to warm up“. This decreased appetite can reduce daily calorie intake.
“There may be a weight loss effect, in this case, linked to eating less“. The benefit can, however, disappear quickly if usual meals are replaced by very sugary products. The doctor warns: “But not if you replace your meals with ice cream or sugary drinks.“
“Heat does not in itself make you lose weight. To lose fat, you must maintain a regular calorie deficit over time, with a balanced diet and appropriate physical activity.“