Fat as Fuel

What is the keto diet?

The amount of fat one eats on a ketogenic diet varies, but the range is typically 75 percent fat, 20 percent protein and 5 percent carbs. To put that into perspective, a woman eating 1,800 calories a day would eat 150 grams of fat, 90 grams of protein and 22 grams of carbs.

The major drawback is that it takes longer and requires more energy to utilize fat instead of stored carbohydrates. Still, many scientists are exploring this possibility by feeding athletes a high fat and low carbohydrate diet to observe changes in metabolism and performance.

The Research

A recent study looked at the effects of the ketogenic diet on physical fitness, body composition and fat metabolism in healthy adults. Forty-two healthy people with an average age of 37 followed a ketogenic diet for six weeks. Seventy-two percent of their calories came from fat, 21 percent came from protein and 7 percent was from carbohydrates.

After six weeks, the researchers measured each subject’s exercise performance and found that their oxygen uptake (or aerobic endurance) decreased by 2.4 percent and the individuals became exhausted more quickly. Additionally, their LDL-cholesterol (or “bad cholesterol”) rose by 10.7 percent. Both of those results are bad signs for the ketogenic diet.

Another study examined how these results differed in well-trained athletes. This small study contained eight male subjects with an average age of 28 and at least five years of training experience. For four weeks, the subjects consumed either a ketogenic diet of 70 percent fat, 15 percent protein and 15 percent carbohydrates or a standard diet of 50 percent carbohydrates, 30 percent fats and 20 percent protein.

The athletes on the ketogenic diet actually experienced a decrease in BMI and body fat, compared to those on the standard diet. Interestingly, their aerobic capacity was significantly higher at rest and during low- to moderate-intensity exercise. This effect reversed during the final stage of exercise, demonstrating that carbohydrates are the main source of fuel during high intensity workouts.

In Closing

Remember that fat is higher in calories than carbs or protein– there are nine calories in a gram of fat while there are only four in a gram of carbs or protein, so if you increase your fat intake, you may actually need to eat less. Another fact to consider: saturated fat has been linked to heart disease and high blood pressure, so it’s important to choose fats that are high in unsaturated fat, such as fish, nuts, oils and avocados.