Any carbohydrates (except vegetables) will stimulate insulin, which nullifies the fat-burning hormones. This means if you consume sugars 1 hour before or during exercise, you can inhibit the entire purpose of exercise fat burning.

Think about this if you exercise moderately for 1 hour, you might burn 350 calories. That’s equivalent to several teaspoons of salad dressing. No big deal!

The real benefits of exercise occur one to two days later, but only if the environment is almost perfect. In other words, if you do things correctly and don’t violate the fat-burning environment, you will burn fat. Fat-storing hormones can easily nullify the fat-burning hormones. The worse off your hormone health, the more perfect the other factors need to be.

What you eat before, during and after

Any carbohydrates (except vegetables) will stimulate insulin, which nullifies the fat-burning hormones. This means if you consume sugars 1 hour before or during exercise, you can inhibit the entire purpose of exercise fat burning. Since fat burning can only occur in the absence of carbohydrates, consuming carbs 14 to 48 hours later can also inhibit fat burning. Drinking several alcoholic beverages can set the liver’s function back for days, preventing fat burning.

Protein before workouts is best.2 Eat an egg, some nuts, a small piece of fish or some cheese before exercising.

I had a patient who would reward herself for exercising by going to Dairy Queen every day and wondered why she wasn’t losing weight. I had another who would drink half a glass of wine before bed, at the same time working out intensely with no results I wonder why? Consuming sugar, juice or refined carbohydrates before bed can inhibit fat-burning hormones while you sleep.

The important thing to remember is that a very small amount of carbohydrates through the day can keep you out of fat-burning mode.

From The 7 Principles of Fat Burning