Once you know what you need to eat to maintain your weight, you can determine what you need to do to gain or lose weight. Whenever you exceed your maintenance needs by 3,500 calories, you gain one pound; when you consume 3,500 fewer calories than you need for weight maintenance, you lose one pound.
If you need 2,000 calories a day to maintain your current weight and you eat 2,500 calories a day for a week, you will gain a pound in that week. Similarly, if you need 2,000 calories a day but consistently consume 2,100 calories a day, you will gain a pound every 35 days. As long as you exceed your needs and consume extra calories, you will gain one pound once you hit the 3,500 additional calories.
To lose one pound of weight, you must consume 3,500 calories less than you need to maintain your weight, but don’t try to do this in one or two days. The guidelines of most major health organizations are to lose one to two pounds per week so that you lose fat and not just muscle. To lose one pound in a week, you would need to consume 500 calories fewer than normal each day for seven days, giving you a cumulative deficit of 3,500 calories (500 x 7 = 3,500). To lose two pounds a week, you would need to cut out 1,000 calories per day, giving you a deficit of 7,000 calories (1,000 x 7 = 7,000). If your maintenance calories were 2,000 per day and you ate 1,500 per day for seven days, you would lose one pound. If your maintenance calories remained the same and you ate 1,000 calories per day, you would lose 2 pounds.
As you lose weight, you need fewer calories to maintain your weight. While there are no firm guidelines on how often to recalculate your BMR, a rule of thumb is to recalculate if you have been at a weight-loss plateau for two to three weeks in spite of being consistent with your eating and activity.
If weight loss can be boiled down to a simple math calculation, why is 65% of the US population overweight? Because it’s actually not that simple, as anyone who has tried to lose weight already knows. Successful, long-term weight loss and maintenance requires making changes in your diet, your behavior, and your level of physical activity. However, it doesn’t require eating less food.
How it is that possible? It all starts with something called energy density. Energy density is the amount of calories in a fixed weight of food. A food with high energy density has a lot of calories in a small amount of food. Foods with very low or low energy density have a small amount of calories in a large amount of food.
The calculation to determine the energy density of food is calories ÷ grams. For example, look at the food label for butter . To determine the energy density of butter, divide 102 calories per serving by 15 grams to get an energy density of 6.8, making butter a very energy-dense food. As seen in the “Energy Density of Foods” table, foods can be categorized according to their energy density.
What affects the energy density of foods the most is water content. Water has an energy density of 0, so it makes sense that it lowers the energy density of food. Foods that contain a lot of water include vegetables, fruits, low-fat dairy products, and soups. If you remove the water from fruit, the energy density increases. Raisins, for example, provide 100 calories per 1/4 cup, while grapes, which are essentially raisins plus water, provide 100 calories in nearly 2 cups.
The more energy-dense foods you eat, the more calories you will take in, so it would seem logical to just eat smaller portions. But as many people have no doubt found, if you’re accustomed to eating 2 cups of grapes, 1/4 cup of raisins isn’t as satisfying.