Bad Research Adds to Our Confusion By Saying Exercise Before Breakfast is Good

A recent study (click it to enlarge the image) showed that your metabolism is higher, so you burn more body fat, while on a Holiday diet (high-calorie and high-fat) if you exercise in the morning before eating anything.  Sounds great until you look at the details of how the study was done.  The researchers compared people exercising that either had not eaten or that had spiked their blood sugar with 675 Cal of carbohydrate at breakfast and then gorged on 200 Cal of sugar per hour during the exercise.  Excess carbohydrate consumption forces insulin to send blood sugar to fat cells.  Fat cells then rob all the sugar from, and stop sending fats into, the bloodstream because they interpret all the insulin as a signal that the blood is overloaded with fuel.  For example, Gail Butterfield showed in a paper over 10 years ago ["Pre-Exercise Carbohydrate Meals: Application of Glycemic Index", DeMarco HM et al., Med Sci Sports Ex 31 (1999) 164] that eating fast-digesting carbs (corn flakes) was much worse for metabolism and performace than eating slower digesting carbs (All Bran) before exercise: The faster-digesting corn flakes cut the amount of fat burned during the workout in HALF, raised the athlete's pain levels, and made them fatigue faster.  This was true even though the total amount of carbs between the two groups was the SAME.  Now imagine having fast-digesting carbs in a LARGER amount (675 Cal) and adding excess sugar during the workout as well: this will totally sabotage the workout and the body's metabolism, driving the body into insulin resistance, higher body fat, and greater disease risk.  My advice: Always consume both carbohydrate and protein before your workout but do NOT spike your blood sugar.  The "benefits" of exercising without eating are relative to an absolutely horrible breakfast (the equivalent to two bagels or a half dozen slices of bread).  Science like this adds to the misinformation and confusion of nutrition, making healthy eating harder for society, not easier.  It reminds me of all the scientific papers showing the benefits of high protein diets when none of them comment on the fact that such benefits are compared to high-carb diets that cause insulin resistance.  When compared to slow-digesting carboydrates (whole grains, whole fruit, vegetables), high-protein diets make you much LESS healthy.  Thank you to Ashish for making me aware of the starving exercise paper.