A 2017 study published in The Journal of Physiologyfound keto hurts athletic performance more than a high-carbohydrate diet or one that includes periods of high carbs and low carbs . On those higher-carb days, Devine recommends sticking to healthy carbs with low amounts of sugar rather than going on a full-blown carb binge. Foods like fruit, sweet potatoes, and whole grains rather than white bread and sweets will make it easier for the body to adapt to ketosis again.
The keto diet is actually known to benefit risk factors for cardiovascular disease. In a study of 83 obese individuals, a long-term keto diet significantly reduced triglycerides and LDL cholesterol and increased HDL cholesterol. In other words, the keto diet improved all measured cardiovascular disease risk factors. Don't be surprised if you've been following a keto diet and someone tells you your breath smells a little fruity or "off." This is actually a sign that you are in ketosis.
Keto advocates claim it gives them an edge for athletic performance by turning them into fat-burning machines. The theory put forward is that, in ketosis, you adapt to use stored fat for energy more efficiently – but this is not borne out by research.