How does the body burn fat?

Billions of fat cells exist in all body types, no matter their shape, sandwiched between the skin and muscle tissue. It’s not the amount of fat cells that dictate a person’s weight, though; it’s the size of them, which can fluctuate depending on how much fat they are storing.

So how does this build up of fatty deposits get broken down when you’re working on losing weight? Put simply, it involves a biochemical process, which converts these space-demanding molecules in fat cells into usable energy.

The entire process begins once you start to increase activity levels and reduce calorie intake; calories indicate how much potential energy is in certain foods. By consuming fewer calories than you’re burning, the body will react to the reduction of available energy by producing fat-mobilising hormones, which in turn signal important enzymes, which help break down fat reserves for more energy.

The key enzyme in this process is lipase. Lipase stimulates fat cells so that they release triglycerides (the form of fat within the fat cell). Each triglyceride molecule is then broken down into glycerol and three fatty acids. The glycerol is broken down further by the liver to release energy, while the free fatty acids are transported directly to muscles via the bloodstream. The enzyme lipoprotein lipase helps the muscle cells absorb the fatty acids, which can be burned for extra energy.

Storing fat
How does the body store fat?

Why does losing weight quickly leave you with excess skin?

Skin is incredibly elastic, so in most cases you can expect it to ping back and fit snugly around your new body shape once you’ve lost weight. This is all thanks to a protein called collagen. Collagen enables the skin to stretch, which is why it’s so important as we grow. However, collagen fibres will weaken over time, resulting in wrinkles as we age.

The production of collagen can also be slow, especially when it comes to sudden weight gain or growth, which in turn leads to overstretched skin as well as noticeable stretch marks. As a result of this, significant or very quick weight loss can often leave you with overhanging, excess skin that can only be removed by a surgical procedure.

Losing weight slowly, with a balance of good food and exercise, can help minimise the risk of loose skin, so don’t rush into shedding stones with a quick-fix crash diet.

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