Being overweight is a huge risk factor for many age-related chronic diseases including heart disease and diabetes. ‘Eat less, move more’ is often the advice given to those seeking to lose weight. It’s simple and it works – but as Dr Jason Fung explains, those who succeed using this method often regain their lost weight despite maintaining a low calorie intake.
Why does this happen? The heart of the problem concerns how the body stores energy. The body stores excess energy in two main forms: glycogen, which is quick to access but provides limited storage capacity, and fat, which is harder to access but allows the long term storage of a large amount of energy. It is this stored fat that weight loss strategies aim to get rid off.
The simple philosophy behind eat less, move more is that by making energy expenditure exceed energy intake, the body will be forced to break down its fat stores to make up the energy deficit. This does works initially, but soon the body’s metabolic rate slows down, energy expenditure decreases, and weight starts to increase.
The key factor overlooked by the eat less, move more strategy is insulin. Insulin is a hormone that controls the balance between short term energy storage (glycogen) and long term storage (fat). Low insulin triggers the breakdown of stored fat. However, overproduction of insulin in obesity make this fat store much harder to access, so the body does the only thing it can to compensate for the energy deficit and slows metabolic rate.
In other words, it doesn’t matter how little you eat if your fat stores are ‘locked away’ due to your chronically high insulin levels. In order to lose weight, it is therefore essential to bring insulin down as well. Fasting intermittently is a highly effective way to do this, as completely stopping energy intake, even on alternate days, produces a stronger insulin reduction than calorie restriction.
Differential Effects of Alternate‐Day Fasting Versus Daily Calorie Restriction on Insulin Resistance: https://doi.org/10.1002/oby.22564
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