You have probably heard the term "calorie" used a lot. When talking about food, a calorie is a unit of energy that the food supplies to your body. But when talking about physical activity, a calorie is a measure of the energy that your body uses in performing the activity.

Calorie balance is like a scale. To remain in balance and maintain your body weight, the calories you get from foods must be balanced by the calories you use in normal body functions and physical activity. If you eat more calories than you use, you gain weight. If you "burn up" more calories than you eat, you lose weight.

To find out if you're at a healthy weight for your height, find your Body Mass Index (BMI). Below are the BMI categories for adults:

Underweight = less than 18.5

Normal weight = 18.5-24.9

Overweight = 25-29.9

Obese = BMI of 30 or greater

If you plan to lose weight

If your BMI is in the overweight or obese category, talk with your doctor or a registered dietitian about the best way for you to reach a healthy weight. In general, you want to stick with the Choose MyPlate plan and eat a variety of healthy foods so that you get all the nutrients your body needs. Aim to:

• Eat more fruits, vegetables, and whole grains
• Cut back on meats high in fat (like burgers and hot dogs), greasy fried foods, and sweets
• Drink more water instead of sugary drinks like sodas
• Be more physically active

The Choose MyPlate website can give you tips on how much of each type of food to eat and how much physical activity you should get in order to reach a healthy BMI.

Don't fall for fad diets that make you eat large or small amounts of a certain nutrient, such as no-carb diets or high-protein diets. Although you may lose weight, you'll probably gain it back as soon as you start eating normally again. In the meantime, you may not be getting all the vitamins, minerals, and other nutrients your body needs.

For people who are severely obese (BMI greater than 40) and cannot seem to lose weight by changing their eating and physical activity patterns, weight loss surgery may be an option. The most common type of weight loss surgery limits the amount of food that your stomach can hold. As a result, you can only eat a small amount of food at one time. Many people who have the surgery lose weight quickly. But you still need to adopt healthy eating and physical activity habits in order to keep the weight off. Also, like all surgeries, weight loss surgery has risks and may involve complications.

More information on Food and fitness for a healthy weight from womenshealth.gov

BodyWorks: A Toolkit for Healthy Teens and Strong Families - This program is designed to help parents and caregivers of teens improve family eating and activity patterns. The toolkit gives parents tools to make small, specific behavior changes to stop obesity and help maintain a healthy weight.

Heart Healthy Eating Fact Sheet - This fact sheet provides information on how healthy eating habits can help to reduce the risk of heart disease. It explains what a healthy portion is and how to make heart-healthy food choices.

Overweight, Obesity, and Weight Loss Fact Sheet - This fact sheet defines obesity and explains some of the factors that contribute to becoming overweight or obese. It provides statistics on how many women are obese, explains the serious health problems associated with obesity, and discusses how obese women can lose weight to improve their health.

Physical Activity Fact Sheet - This fact sheet explains the benefits of exercise for people of all ages, how much exercise you should get each day, and when you should talk to your doctor.

Explore other publications and websites

Balancing Calories - This Web page has information on balancing your calorie intake with exercise. It also has a question and answer section about calories.

Dietary Guidelines for Americans, 2010 - This report provides advice about how good dietary habits can promote health and reduce risks for major chronic diseases.

Fit and Fabulous as You Mature - This publication explains why obesity is a health problem for aging Americans. It discusses the benefits of physical activity and the health risks of poor diet and a sedentary lifestyle. It also gives tips for how to become more active and eat better.

Girlfriends' Health and Safety Tips - You and your girlfriends can help each other keep both mentally and physically fit. This fact sheet has information about how you can support and inform the women that are close to you.

Guide to Behavior Change - If you are overweight, making these changes will reduce your risk for health problems including, diabetes, high blood pressure, high cholesterol and triglycerides, arthritis, gall bladder disease, gynecologic problems, some cancers, and lung problems.

Healthy Eating and Physical Activity Across Your Lifespan: Better Health and You: Tips for Adults - This booklet gives information on weight gain and obesity in adults. It also includes information on eating healthy, getting active, and losing weight.

Just Enough for You: About Food Portions - This booklet provides information on the difference between a portion and a serving. It also includes tips on how to control portion size at home and when eating out.

Let's Eat for the Health of It - This brochure has tips to help you build a healthy plate, cut back on unhealthy foods, eat the right amount of calories, and be physically active.

My Bright Future: Physical Activity and Healthy Eating for Adult Women - This booklet will help you learn more about the importance of physical activity and healthy eating in your daily life. It will also help you talk with your doctor about these topics and set health-related goals. Included are personalized tip sheets that can help you meet your nutritional goals.

Nutrition and Activity Quiz (Copyright © American Cancer Society) - Are you making healthy choices when it comes to nutrition and physical activity? Find out by taking this quick quiz.

Steps to a Healthier Weight: Making Nutrient-Dense Food Choices - This chart lists common foods that are high in solid fat or added sugar and suggests healthier foods to eat instead.

Weight and Waist Measurement: Tools for Adults - This brochure gives information on how you can use your body mass index (BMI) and waist circumference to determine if you are at risk for weight-related health problems, such as heart disease or type 2 diabetes.

Weight-loss and Nutrition Myths - This publication provides information on how to lose weight and maintain a well-balanced diet. It also debunks many popular myths about dieting and weight loss.