How Sugar Causes Weight Gain

Most foods affect the body in different ways. Sugar is one of the main ingredients that can make us fat.

Sugar (sucrose) and high fructose corn syrup contain two molecules: glucose and fructose.

Glucose is absolutely vital to life and is an integral part of our metabolism. Our bodies produce it and we have a constant reservoir of it in the bloodstream.

Every cell in the body can use glucose for energy. If we don’t get glucose from the diet, our bodies produce what we need out of proteins and fats.

Fructose, however, is very different. This molecule is not a natural part of metabolism and humans do not produce it.

In fact, very few cells in the body can make use of it except liver cells.

When we eat a lot of sugar, most of the fructose is metabolized by the liver. There it gets turned into fat, which is then secreted into the blood.

1. Fructose Causes Insulin Resistance

Junk Food

Insulin is one of the key hormones that regulate human metabolism and energy use. It is secreted by the pancreas, then travels in the blood to peripheral cells like muscle cells.

Insulin sends a signal to these cells that they should put transporters for glucose onto their surface, thereby allowing glucose to get into the cells where it can be used.

When we eat a high carb meal, glucose levels go up. Excess glucose is toxic so insulin rapidly goes up in order to get the glucose out of the bloodstream and into the cells.

If we didn’t have insulin or it wasn’t functioning correctly, blood glucose would reach toxic levels.

In healthy people, this mechanism works very well and enables us to eat meals that are high in carbohydrates without our blood glucose going out of whack.

However this mechanism tends to break. Cells become resistant to the effects of insulin, which makes the pancreas have to secrete even more to drive the glucose into the cells.

Basically, when you become insulin resistant, you will have more insulin in your blood all the time.

But insulin also has other functions. One of them is sending signals to our fat cells. Insulin tells the fat cells to pick up fat from the bloodstream, store it and to avoid burning the fat that they already carry.

When insulin levels are chronically elevated, much of the energy in our bloodstream gets selectively deposited in the fat cells and stored.

Excess fructose consumption is a known cause of insulin resistance and elevated insulin levels in the blood.

When this happens, the body has a hard time accessing the stored fat and the brain starts to think that it is hungry. Then we eat more.

2. Fructose Causes Resistance to a Hormone Called Leptin


Fructose also causes weight gain by its effects on a hormone called leptin.

Leptin is secreted by fat cells. The bigger the fat cells, the more leptin they secrete. This is the signal your brain uses to determine how much fat it has stored for a rainy day.

When we eat food, some of it gets stored in the fat cells. This makes the fat cells get bigger and secrete more leptin.

When the brain senses the increased leptin, it “sees” that we have enough fat stored and that we don’t need to eat.

This is the elegant mechanism designed by nature to make us stop being hungry and eat less when there is plenty of fat in the our fat cells, which is supposed to prevent us from becoming obese.

More fat = more leptin = we have enough energy = don’t need to eat. Simple.

Increased leptin also makes us release more fat from our fat stores and raises the metabolic rate.

This is how it’s supposed to work, but if the brain becomes resistant to leptin (doesn’t “see” the leptin in the blood) then this regulatory process won’t work.

If the brain doesn’t see the leptin, it won’t know that the fat cells are full and there won’t be any signal to tell the brain that it needs to stop eating.

Low leptin = don’t have enough energy stored = the need to eat more and burn less.

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