Where Does Your Fat Go When You Lose Weight? 

When you start dieting and increasing your exercise you may notice that over time your clothes start feeling looser. This is certainly a welcome sign, but how does this happen? There are plenty of people trying to lose weight today with methods ranging from exercise, dieting or even surgery, all with the goal of achieving a smaller size. But how do these methods make your body smaller and where does your fat go when you lose weight?

Where does your fat go when you lose weight?

In short, the fat cells are converted into forms of energy the body can use, shrinking these cells. Understanding how this process works can help you find the most effective ways to lose weight.

Losing weight is actually a fairly complex biochemical process. All fats are known chemically as triglycerides, which are made up of three fatty acid trains and a glycerol molecule. These triglycerides are made up in the letter "E," with glycerol making up the vertical line and the fatty acids composing the three horizontal lines. These molecules are typically stores as oils within the fatty tissue in the body. These are meant to act as fuel that will help you gain the energy to take on the day's activities, the way a gasoline tank fuels a car.

Those who are overweight have fat cells that have excess amounts of triglyceride oil stored inside. When you diet and cut calories out of your diet or increase your exercise levels, the hormone sensitive enzyme lipase that is located within these fat cells will note the hormonal messages triggered by these activities. Responding to these messages, the lipase will start breaking down the triglycerides into their fatty acid and glycerol components. These will then leave the fat cells and enter the bloodstream, so the tissues throughout the body can use them. The liver will then absorb the glycerol and some of the fatty acids, sending the rest to your muscles.

Once these triglyceride components enter the muscles and liver, they will be broken down further and modified as necessary, eventually creating a store of compounds of acetyl-CoA. The cell's powerhouses, the mitochondria, will combine these acetyl-CoA stores with oxaloacetate, creating citric acid. This will start the citric acid or Krebs cycle, which creates energy the body can use from carbohydrates, proteins and fat. As this cycle moves on, water, heat, carbon dioxide and adenosine triphosphate (ATP) will be created. ATP is an energy-carrying molecule that helps the body fuel cellular activities.

The carbon dioxide created through the Krebs cycle is expelled through the lungs. The excess water will be expired with perspiration or urination. The heat generated by the Krebs cycle is used to help maintain a healthy body temperature. Finally, the ATP powers any cells in your  body that need energy, including the muscles you are using to exercise, your heart which is beating and the muscles in the digestive system that are helping you take in and break down food to create more energy.

What happens to your skin when you lose weight?

While your clothes tend to be looser when you start losing weight, so does your skin. If you are only losing a moderate amount of weight, your skin will simply shrink to match your new body size. The skin is elastic so it is easy for it to expand and contract within a certain limit. Proteins known as collagen help the skin maintain this elasticity so that the skin can grow with our bodies as we age. However, over time this collagen breaks down, causing the skin to wrinkle.

Stretch Marks

There are limitations on how much stretching collagen can manage. If you gain or lose a great deal of weight quickly, your collagen may not be able to keep up with these activities, causing the skin to overstretch. When you gain an excessive amount of weight, stretch marks will appear due to this fast paced growth. Those who are going through puberty or pregnancy are at an increased risk for developing these marks.

Excessive Skin

Those who lose a great deal of weight very quickly will typically have a lot of leftover skin that remains from their heavier shape. This skin has become so overstretched that it now simply hangs, similar to an over-worn piece of elastic. People undergoing gastric bypass surgery are at an increased risk for developing this excess skin and will typically need additional procedures to surgically remove this excess skin from their bodies as well.

It is important to address this excess skin on the body after a great deal of weight loss. This excess skin has an increased risk of rash, infection and can cause back problems.