A calorie is a unit of energy that food provides. The calories in the food you eat come from its carb, protein and fat content: 1 gram of carbohydrate or protein provides 4 calories, and 1 gram of fat provides 9 calories. While each of these nutrients serves a different purpose in your body, when it comes weight loss or gain, what matters most is the total calories.
To lose weight, your total caloric intake needs to be less than the amount your body needs; this encourages your body to burn fat for energy. If you can create a 3,500-calorie deficit per week, or 500 calories a day, you can burn off 1 pound of fat per week. For example, if you require 2,000 calories a day to maintain your current weight, you need to reduce your intake to 1,500 calories to lose.
When it comes to weight loss, carbs are sometimes on the “no-no” list. But carbs should actually make up the bulk of your caloric intake — 45 to 65 percent — according to the 2010 Dietary Guidelines from the U.S. Department of Health. However, not all carbs make good choices on a weight-loss diet. You might have more success losing weight and keeping it off by filling your diet with healthy, unprocessed carbs such as whole grains, fruits and vegetables, rather than processed carbs such as white bread and pasta, sweets and soda, according to the Harvard School of Public Health. A 2011 prospective study published in the “New England Journal of Medicine” found that weight gain was associated with intake of unhealthy carbs and weight loss with eating healthy ones. On a 1,500-calorie diet, 675 to 975 of those calories should come from carbs. That’s around 170 to 245 grams daily. The range allows you to create a healthy diet that suits your personal taste.
Many popular weight-loss diets encourage you to eat more protein to lose weight. While a 2011 study published in The Journal of the American Medical Association found that people following a high-protein, high-fat, low-carb diet lost more weight than those following a low-fat diet. However, the long-term effects of following a low-carb diet are not not known, making it a difficult diet to recommend. For good health, the dietary guidelines recommend 10 percent to 35 percent of calories come from protein. On a 1,500-calorie diet, 150 calories to 525 calories should come from protein. That translates to 38 to 131 grams of protein per day, but strive for the higher end, as most women need a minimum of 46 grams of protein per day, even on a lower-calorie diet.
Quality also counts when it comes to protein foods and weight loss. Get your protein from healthy sources such as lean meat, poultry, fish, eggs, beans, soy and low-fat dairy on your weight-loss diet.
Like carbs, fat is often omitted from the diet as a means to help with weight loss. Part of the rationale for the restriction is that fat is a concentrated source of calories. However, fat is an important part of your diet, and like the other two macronutrients, the dietary guidelines offer a range for the amount of calories you should get from fat: 20 percent to 35 percent, or 300 calories to 525 calories on a 1,500-calorie diet, for overall good health. That’s 33 to 58 grams of fat per day. Your fat choices should come from healthy sources when you’re following a weight-loss diet, such as vegetable oils, avocados and nuts.