Converting Fat to Energy—Fueling Your Body for Exercise Menu Verywell Fit Nutrition Weight Management Nutrition Facts Nutrition Basics Diets Meal Plans Meal Delivery Services View All News Fitness and Nutrition What to Buy How We Test Products Fitness Gear Nutrition Products Tools Recipe Nutrition Calculator Weight Loss Calorie Goal BMI Calculator Body Fat Percentage Calculator Calories Burned by Activity Daily Calories Burned Pace Calculator About Us Editorial Process Meet Our Review Board Search Sports Nutrition Converting Fat to Energy During Exercise By Elizabeth Quinn Elizabeth Quinn Elizabeth Quinn is an exercise physiologist, sports medicine writer, and fitness consultant for corporate wellness and rehabilitation clinics. Learn about our editorial process Updated on October 12, 2021 Medically reviewed Verywell Fit articles are reviewed by board-certified physicians and nutrition and exercise healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by Barbie Cervoni MS, RD, CDCES, CDN Medically reviewed by Barbie Cervoni MS, RD, CDCES, CDN Barbie Cervoni MS, RD, CDCES, CDN, is a registered dietitian and certified diabetes care and education specialist. Learn about our Medical Review Board Print Getty Images / Science Photo Library Table of Contents View All Table of Contents Understanding Dietary Fat How the Body Uses Fat for Fuel Popular High-Fat Diets Fat is an important component of a diet designed to fuel exercise. One gram of dietary fat equals nine calories, and one pound of stored fat provides approximately 3,600 calories of energy. This calorie density (the highest of all nutrients), along with our seemingly unlimited storage capacity for fat, makes it our largest reserve of energy. These calories are less accessible to athletes performing quick, intense efforts like sprinting or weight lifting. But fat is essential for longer, slower, lower intensity and endurance exercise, such as cycling and walking. Understanding Dietary Fat Everything we eat is made up of macronutrients (protein, carbohydrates, and fat) and micronutrients (vitamins and minerals). These are converted to energy inside the body, helping to fuel all of our bodily functions. Dietary fat has been blamed for many health problems, but it is actually an essential nutrient for optimal health. Adipose tissue (stored fat) provides cushion and insulation to internal organs, protects nerves, moves certain vitamins (A, D, E, and K) throughout the body, and is the largest reserve of stored energy available for activity. Stored body fat is different from dietary fat. Body fat is only stored in the body when we consume more calories than we use, from any and all foods we eat, not just from dietary fats. There is an optimal level of body fat for health and for athletic activity. How the Body Uses Fat for Fuel Fat provides the main fuel source for long-duration, low- to moderate-intensity exercise (think endurance sports, such as marathons). Even during high-intensity exercise, where​ carbohydrate is the main fuel source, the body needs fat to help access the stored carbohydrate (glycogen). Using fat to fuel exercise, however, is not a simple process. It has three key parts: Digestion: Fat is slow to digest and be converted into a usable form of energy. This process can take up to six hours.Transportation: After the body breaks down fat, it needs time to transport it to the working muscles before it can be used as energy.Conversion: Converting stored body fat into energy takes a great deal of oxygen, which requires decreased exercise intensity. So athletes need to carefully time when and how much fat they eat. In general, it’s not a great idea to eat foods high in fat immediately before or during intense exercise. First, the workout will be done before the fat is available as usable energy. And second, doing so can cause uncomfortable gastrointestinal symptoms, such as nausea, vomiting, and diarrhea. Popular High-Fat Diets Popular low-carbohydrate and high-fat diets, such as the ketogenic diet and Paleo diet, all work on the same premise. The theory is that lower carbohydrate intake, coupled with high fat and moderate to high protein intake, leads to burning body fat as the main fuel source while exercising. There is, in fact, some scientific evidence that long-term low-carb/high-fat diets are safe and may help improve metabolic risk factors for chronic disease. In studies, these diets have shown to be beneficial for performance in ultra-endurance sports—but at least several months of adaptation to a low-carb/high-fat diet are required for metabolic changes to occur. 1 Source Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Chang CK, Borer K, Lin PJ. Low-carbohydrate-high-fat diet: Can it help exercise performance?. J Hum Kinet. 2017;56:81-92. doi:10.1515/hukin-2017-0025 Additional Reading Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Nutr Diet. 2000;100(12):1543-1556. doi:10.1016/s0002-8223(00)00428-4 By Elizabeth Quinn Elizabeth Quinn is an exercise physiologist, sports medicine writer, and fitness consultant for corporate wellness and rehabilitation clinics. See Our Editorial Process Meet Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit Related Articles Why Your Body Needs Glycogen The Macronutrients Your Body Needs Most 13 Tips for Fuel and Hydration While Running, According to Experts How Does Fat Leave the Body When You Lose Weight? How Do Low-Carb Diets Affect Your Cholesterol and Triglycerides? How Can I Burn More Fat When Exercising? Pros and Cons of Weight Training on an Empty Stomach What to Eat Before, During, and After You Run How Do Carbs Fuel Exercise? How Your Body Turns Food Into Fuel Is Sugar Addictive or Just Rewarding: A Closer Look at the Research What is Nutrition and Why Does it Matter? The Truth About Your Fat-Burning Zone for Weight Loss Improving High-Intensity Endurance With Lactate Threshold Training The Best Electrolytes for Runners, According to a Dietitian Anaerobic Metabolism vs. Aerobic Metabolism in Exercise When you visit the site, Dotdash Meredith and its partners may store or retrieve information on your browser, mostly in the form of cookies. Cookies collect information about your preferences and your devices and are used to make the site work as you expect it to, to understand how you interact with the site, and to show advertisements that are targeted to your interests. You can find out more about our use, change your default settings, and withdraw your consent at any time with effect for the future by visiting Cookies Settings, which can also be found in the footer of the site. Cookies Settings Reject All Accept All