Keto and Resistance Training

The keto diet can pair well with exercise, maximizing fat loss and increasing lean body mass. There is, however, a debate surrounding how it functions with high-intensity exercise, which typically is fueled by the glucose from carbohydrates. Many athletes looking to build muscle mass will ‘carb-up’ before training or events.

When switching to keto — especially from the carb-heavy standard American diet — your body needs time to adjust to getting energy primarily from fats. During this transition period, you may notice a decrease in energy or performance. Eventually, your body can begin making some of the glucose it would have needed for these workouts from fats and proteins through a process called gluconeogenesis. A keto-adapted body is just as primed for muscle-building as one on a carb heavy diet — but studies have shown that the fat-burning of a keto diet is much more effective at taking off body fat while building muscle.**

Exercise and Estrogen

Hormones play many roles in metabolism, but one important consideration for women looking to lose weight and/or build muscle is how estrogen affects fat storage. In females, estrogen is primarily produced by the ovaries, the placenta (during pregnancy), and in smaller amounts by the liver, the adrenal glands, and the breasts. However, fat cells also produce estrogen. Because estrogen promotes fat storage, the production of estrogen by fat cells increases as body fat increases, creating a vicious runaway effect. This is one of the reasons that it can get harder and harder to lose weight once you’ve put it on.

When at a good level of weight loss ketosis, the impact of estrogen is lessened because your fat-burning system is fully activated. The estrogen competes with the fat-burning, meaning less and less of the fat actually ends up deposited.

In the first two weeks of the menstrual cycle (with day one being the start of your period), your body’s production of estrogen is at its lowest — but this also means that your ability to burn fat is at its highest! Try pushing your cardio and resistance workouts during these two weeks to burn extra fat. However, if you are on any sort of hormonal therapy or contraception, your estrogen production will be increased, likely preventing you from taking advantage of these low points.

Volek et al. 2016. "Metabolic characteristics of keto-adapted ultra-endurance runners." Metabolism 65, 3: 100–110.

Phinney et al. 1983. "The human metabolic response to chronic ketosis without caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation." Metabolism 32, 8: 769–776.