Does intermittent fasting work for weight loss?Intermittent Fasting (IF) is an eating approach in which you go without eating for 12-18 hours straight. Let’s say you have your dinner at 6 pm and your next meal is breakfast at 8 am – you’ve just passed 14 hrs without eating.
Many people claim that IF helps them with:
❗️significant weight loss,
❗️improved insulin sensitivity and
❗️blood pressure and even skin and vision!
In theory it makes sense – since hormone insulin is released in response to eating (particularly carbohydrate and to some extend protein rich meals) and this same hormone is then responsible for storing extra calories as fat, the drop in insulin would result in either weight stabilization or loss. Is that so?
Between meals, as long as we don’t snack, our insulin levels will go down and our fat cells can then release their stored fat, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.
However, without any reduction in calories the weight won’t budge even with significant health benefits brought upon by the IF. With every next meal, if you are not reducing calories, fat cells will be restocked and weight will be maintained (or increased!).
A study recently published in Science Direct looked at overweight men with prediabetes undergoing Time Restricted Feeding (a type of IF) and found that indicators of metabolic health (insulin sensitivity, blood pressure, oxidative stress) had improved significantly even without any weight loss.
Another study that involved overweight and obese postmenopausal women, focused on their body composition and metabolic profile. They were randomized into 3 groups: IF, Continuous Diet and no treatment (control group). When researchers compared short- and long-term effects, there were no differences in weight loss between IF and continuous diet, while both treatments were more effective for weight loss than in no treatment group. While fasting glucose was lower in the IF group as a short-term effect, the difference was no longer present at long-term follow up.
So it is clear that weight loss without caloric restriction will not take place. Even if you starve yourself for 18 hours straight, overeating in the remainder 8 hours will result in weight gain. Although it’s rather hard to eat your daily caloric needs in such short period of time, and that’s where the catch with IF is – you end up eating less.