In trained male cyclists, switching to a diet with very little carbohydrate for seven days lowers average glucose levels in the body and reduces fluctuations in glucose compared to a diet high in carbohydrates.

Among trained male cyclists, consuming a diet high in carbohydrates results in a higher amount of time during exercise with blood glucose levels between 121 and 180 mg/dL compared to a low-carbohydrate diet, reflecting larger increases in blood glucose after eating and training.

When trained male cyclists follow the same diet and exercise routine, their blood glucose levels can vary by as much as 30 mg/dL between individuals, suggesting that a one-size-fits-all nutrition approach may not be effective for everyone.

After eating just three days of mostly fatty food instead of carbs, healthy young men had higher blood sugar spikes when they drank a sugary drink, meaning their bodies handled sugar less efficiently.

When healthy young men ate the same number of calories but swapped carbs for fat for just three days, their body’s response to sugar changed—blood sugar went up, insulin came out slower, and a gut hormone went up.

If untrained guys eat a high-fat diet for 7 weeks, their muscles use less stored sugar during medium-intensity exercise compared to eating a high-carb diet — it’s like saving their fuel — but their legs still take up the same amount of glucose from the blood.