What happens to body fat when you lose weight—do you sweat, urinate, or exhale? The answer is yes.
How did this happen? It helps to understand that our bodies are designed to store excess energy in fat cells.
If you are overweight, it means you are taking in more energy units than you are using .
Excess energy is stored in the fat tissue around the body in the form of triglycerides. Small amounts of energy are stored in the liver and muscles in the form of glycogen.
How does your body use energy? In more ways than you think:
- When you rest. Your heart needs energy to pump blood, your lungs need energy to breathe, and your brain needs energy to think. (This is your basal metabolism.)
- When you are active. Whether you're just standing up from a chair or running a marathon, your muscles need energy.
- While you are eating. Your digestive system needs energy to break down and store food.
What happens to body fat when you diet?
When you diet, you eat fewer calories than your body needs. Because of this deficiency, your body taps into fat reserves for energy.
Your body must deal with fat deposits through a complex series of metabolic pathways.
The by-products of fat metabolism leave your body:
- As water, passes through your skin (when you sweat) and your kidneys (when you pee).
- As carbon dioxide (CO2), passes through the lungs (when you breathe out).
At the same time, lipolysis releases energy for biological functions and physical activity. It also generates heat to keep body temperature normal.
What happens to body fat during exercise?
Your muscles first burn stored glycogen for energy. After about 30 to 60 minutes of aerobic exercise, your body begins to burn primarily fat. This should take about an hour if you're doing moderate exercise.
Experts recommend at least 30 minutes of aerobic exercise two to three times a week.
They also recommend weight lifting and resistance training. Building muscle mass can help you burn more calories and increase your basal metabolic rate.
Exercise also increases your breathing rate, so more carbon dioxide leaves your body during exercise.
About exercise and weight loss
Exercise is key to losing weight and maintaining weight loss.
But it may take some time to move the number on the scale, so be patient.
Everyone responds differently to exercise: Some people lose weight, some stay the same, and some may even gain a few pounds.
In general, however, people who successfully lose weight and keep it off tend to be physically active—up to an hour a day. Some form of exercise three times a week is highly recommended.
If you're unsure about how to incorporate fitness into your daily life or have questions about diet and healthy weight, it's best to contact a health care provider or nutritionist first.