Losing weight can be stated in a simple way. If you consume more calories than you burn you will gain weight. If you consume less calories than you burn you will lose weight. Burning calories does not mean "working out". The primary way your body burns calories is through your metabolism. The higher your metabolism the more likely it is you will lose weight.
Metabolism is the process in which the body turns nutrients into energy. Metabolic Rate is the rate at which your body burns calories. Many have heard the terms "fast" and "slow" used with metabolism. It is not just a matter of genes, you can do something to raise your metabolic rate and burn more calories.
The first thing that affects your metabolism is your resting metabolic rate, or RMR. This is the number of calories you burn while sitting around doing absolutely nothing. This number accounts for 60-75% of your metabolism. It is this number that you want to be as high as possible.
It is important to exercise regularly. Regular exercise will raise your metabolic rate in two ways. First, muscle tissue uses more energy than fat tissue. So, the more muscle tissue you have the more calories you are going to burn. Second, cardio allows your body to use oxygen more efficiently. This in turn ups your metabolic rate.
It is important to eat 4-6 small meals throughout the day as opposed to 2-3 large meals. This way your body avoids "starvation mode". When you are constantly taking in just enough nutrients to fuel the body, your metabolism stays steady and constant. Eating larger meals slows your metabolism.
"Starvation Mode" is when your body slows your metabolic rate and stores the food you are eating as fat. The body knows you will not be eating again for hours and it wants to save as many calories as possible. These calories are stored and lead to weight gain. This can be avoided by eating small meals often. Then the body does not need to store calories. It knows that you will be eating again shortly, and there is no need to store calories.
A balanced diet is also helpful. Since the body burns nutrients at different rates, it is beneficial to get a balance of carbs, protein, and fat. This will allow you to maintain your energy level until your next small meal. First your body will burn the simple carbs for quick energy, then the proteins, and then finally, the fat is last to burn. Since you have only small amounts of each, nothing is stored and everything is used. By this time you are hungry for your next small meal.
Finally, breakfast is incredibly important. This accounts for 25% of your metabolism. Without breakfast your body will burn calories less efficiently the entire day. Breakfast is what gets your metabolism going. Without it your metabolic rate never gets started properly. This leads to weight gain. For more information see the article The Importance of Breakfast.