Athletic Performance on a Low-Carb, High-Fat Diet

salmon avocado nuts olive oil

Are you thinking about trying a low-carb, high-fat diet? Some people have tried it for weight loss. Others go on an extreme low-carb diet to treat a health condition, such as epilepsy. Studies also show that the low-carb, high-fat diet may potentially enhance athletic performance, with the body’s ability to adapt to burning fat for fuel—and then burn the vast stores of fat for long periods of time without the need to “reload” on calories.

Overview of a Low-Carb, High-Fat Diet

According to the Mayo Clinic, a low-carb diet limits carbohydrates to 60 to 130 grams a day. This is up to 265 grams of carbs less than the recommended carb intake for a 2,000-calorie diet. It requires a significant modification of the typical American diet: Eating one large banana (which contains 31 grams of carbs) and one packet of instant oatmeal (which contains 27.5 grams of carbs) for breakfast would instantly max out a carb load for the day if the limit was 60 grams a day.

With a decrease in carbs, the body needs another source of fuel. While protein can be broken down for energy, the body prefers to use protein for building muscle and carrying out other important functions for health. So fat is thought to be the best alternative energy source. The amount of fat that should consumed each day depends on the number of carbs in the diet. It’s important to maintain an adequate calorie intake during and after the transition from high carb to high fat.

It can take several weeks for the body to adjust to a high-fat diet. During the first few weeks, symptoms such as sluggishness or brain fog are common. Because more serious side effects (see below) can occur with this diet, partner with your doctor to determine whether it’s the right choice for you.

Sources of Healthy Fat

Not all fat is created equal. Trans fats, which are often called “partially hydrogenated oil,” should be avoided if at all possible. These fats can be found on the ingredients lists of processed foods—including fried foods, baked goods, and chips. Trans fat can increase your cholesterol and potentially lead to cardiovascular disease.  

The following list contains healthy, natural fats that can be included in a high-fat diet:

  • Nuts
  • Avocados
  • Olive oil
  • Sardines and salmon
  • Flax seed
  • Coconut milk

Note: Some of these foods are high in saturated fat. Although saturated fat has been thought of as a potential contributor to cardiovascular disease, studies show that it can, in limited quantities, provide health benefits. Each individual is different, and it is important to seek advice from a health professional for any diet modification.

The Low-Carb, High-Fat Diet and Athletics

In an essay published in the British Journal of Sports Medicine in 2014, Timothy Noakes, Jeff S. Volek, and Stephen D. Phinney questioned the validity behind the standard advice to load up on carbs before and during exercise. They noted that humans have the ability to adapt to effectively burning fat for fuel, as demonstrated by generations of humans surviving in the Arctic by eating mostly animal fat. They postulated that burning the abundant fat stores in the body for fuel during prolonged exercise could improve energy production and athletic performance. (A slender body with as little as 7 to 14 percent body fat can store 30,000 to 60,000 kcal of fat and, by comparison, it can store only 2, 000 kcal of carbs.)

The authors of this essay could only find 11 studies done within the last 31 years showing how low-carb diets affect athletic performance. In nine of these studies, a low-carb diet either improved performance or made no difference. Two of the studies showed adverse effects related to a low-carb diet. The authors noted that none of the studies allowed for long-term adaptation to the diet; giving athletes time to adapt to the diet could increase its positive effects.  

Research conducted in 2015 (after the essay above was published) provided ultra-endurance athletes adequate time (20 months) to adapt to a low-carb diet. The diet consisted of 10 percent carbs, 19 percent protein, and 70 percent fat. The study showed that the athletes on a low-carb diet were more than two times more effective at burning fat than the high-carb athletes.

The high-carb paradigm for athletics may be shifting now as research continues to show that consuming high amounts of carbs may not be the ideal dietary strategy for generating energy for athletes, especially those in endurance sports.

Potential Risks of a Low-Carb Diet

Despite the potential benefits, a low-carb diet comes with risks, too. Cutting carbs too quickly can cause weakness, headaches, fatigue, and gastrointestinal distress. A low-carb diet can cause bone loss, nutrient deficiencies, and increased risk for certain diseases. As mentioned above, a diet high in saturated fat can potentially contribute to cardiovascular issues. Not enough studies have been run to be really clear on all the long-term effects of this diet.

If you’re thinking about trying a low-carb, high-fat diet, check with your doctor first to discuss the risks and benefits and to ensure you are receiving adequate nutrition with the new diet.


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*Editor’s Note: The information in this article is intended for your educational use only; does not necessarily reflect the opinions of the Chopra Center's Mind-Body Medical Group; and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health providers with any questions you may have regarding a medical condition and before undertaking any diet, supplement, fitness, or other health program.

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About the Author

Valerie Sjoberg, L.Ac.

Acupuncturist, Holistic Health Coach, Writer, and Editor
Valerie’s interest in healing began in her early twenties when doctors told her she would need to give up running and other physical activities forever due to debilitating back injuries. This spurred an exploration into mind-body and alternative medicine, which ultimately healed her back and allowed her to resume the activities she loved. Today, she works as an acupuncturist and health coach to help activate others’ self-healing abilities, and is inching toward a master's degree in nutrition and functional medicine. She is also a professional writer and aims to accumulate enough words and inspiration to write a novel someday.Read more