(MayoClinic.com) Despite all the diet strategies out there, weight management still comes down to the calories you take in versus those you burn off. Fad diets may promise you that avoiding carbs or eating a mountain of grapefruit is the secret to weight loss, but it's really all about calories.

Calories are the energy in food. Your body has a constant demand for energy and uses the calories from food to keep functioning. Energy from calories fuels your every action, from fidgeting to marathon running.

Carbohydrates, fats and proteins are the types of nutrients that contain calories and are the main energy sources for your body. The amount of energy in each varies. Proteins and carbohydrates have about 4 calories a gram, and fats have about 9 calories a gram. Alcohol also is a source of calories, providing about 7 calories a gram.

Regardless of where they come from, the calories you eat are either converted to physical energy or stored within your body as fat. These stored calories will remain in your body as fat unless you use them up, either by reducing calorie intake so that your body must draw on reserves for energy, or by increasing physical activity so that you burn more calories.

Your weight is a balancing act, but the equation is simple: If you eat more calories than you burn, you gain weight.

Because 3,500 calories equals about 1 pound (0.45 kilogram) of fat, you need to burn 3,500 calories more than you take in to lose 1 pound. So if you cut 500 calories from your typical diet each day, you'd lose about 1 pound a week (500 calories x 7 days = 3,500 calories).

Cutting calories doesn't have to be difficult. In fact, it can be as simple as:

• Skipping one extra high-calorie indulgence a day
• Swapping high-calorie foods for lower calorie options
• Reducing portion sizes

Here's a closer look.

Skipping one or two high-calorie items is a good place to start when cutting calories. For example, you could skip your morning latte or that bowl of ice cream you always have after dinner. Think about what you eat and drink each day and identify items you could cut out. If you think that skipping your indulgence will leave you with a craving, try a low-calorie substitution.

Healthier options

*Actual calories may vary by brand.

Beyond your indulgences, you can also replace common foods that are high in calories with ones that are lower in calories. You may not realize how much you can cut with some simple substitutions. For example, drink fat-free milk instead of whole milk and sparkling water or diet soda instead of blended coffee drinks. Have an extra serving of vegetables at dinner instead of an extra serving of meat. Or snack on sliced fresh fruit instead of chips.

Lower calorie options

*Actual calories may vary by brand.

The sizes of your portions affect how many calories you're getting. Twice the amount of food means twice the number of calories. It's common to underestimate how much you're eating, especially if you're dining out. Controlling your portions is a good way to control calories.

Portion sizes

*Actual calories may vary by brand.

Try these tips to control portion sizes and cut calories:

• Serve smaller portions. At the beginning of a meal, take slightly less than what you think you'll eat. You can have seconds later if you're truly still hungry.
• See what you eat. Eating directly from a container gives you no sense of how much you're eating. Seeing food on a plate or in a bowl keeps you aware of how much you're eating. Consider measuring your food with a measuring cup or scale to see how much you are actually eating.
• Check food labels. Be sure to check the Nutrition Facts panel and other nutrient information for the serving size and number of calories a serving. You may find that the small bag of chips you eat with lunch every day, for example, is two servings not one, which means you're eating double the calories listed on the label.
• Don't feel obligated to clean your plate. Stop eating as soon as you feel full. Those extra bites of food that you're trying not to waste add unneeded calories.
• Use a calorie counter. Check out reputable resources that offer tools to count calories, such as Web sites or smart phone applications.

Eliminating high-calorie foods, choosing lower calorie alternatives and cutting your portion sizes can help you reduce calories and improve weight control. For a successful — and sustainable — weight management plan, you also need to increase your physical activity. It's this combination of regular activity and healthy eating that will help you achieve and maintain a healthy weight.

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