The Ketogenic Quandary

Should you adopt a low-carb, high-fat diet for performance gains?

- Kylee Van Horn

Despite the high-carbohydrate tradition in running, some endurance athletes are going against the grain and choosing low-carbohydrate, high-fat (LCHF) diets in an attempt to change the way their bodies use energy—using fat stores first and reserving glycogen stores for later. LCHF is a general term, while the name Ketogenic is reserved for a diet high in fat, moderate in protein and very low in carbohydrates (less than 50 grams per day on average). As a result, the body utilizes ketones that are produced from fatty acids rather than glucose for energy.

How Does It Work for Athletes?

While exercising at lower intensities (because the activity is sustained, ultrarunners are typically in the middle range of VO 2 max), fat is utilized more readily by the body and actually produces more energy per gram than carbohydrates. However, as of intensity increases (greater than 70-percent VO 2 max), the body needs more carbohydrates. When carbohydrates are reduced, metabolic changes occur in the body that typically leads to a faster fat-processing rate and slower carbohydrate-processing rate.

Some endurance athletes like Jeff Browning, 47, a coach and the winner of the 2018 Hardrock 100, and Zach Bitter, 33, the American 100-mile record holder, have displayed promising results with this diet as a strategy for maintaining long-term energy over ultra distances; however, the scientific jury is still out.