An article by John Cloud, Why Exercise Won’t Make You Thin on Time.com misses the point of why exercise is important. It is true that exercise only burns an infinitesimal number of calories. If you are into the calories in, calories out frame of mind, you will need to exercise for 10 hours to cover a Big Mac. 20 minutes of jogging barely covers a small chocolate chip cookie. It isn’t even a matter of converting fat to muscle: if you converted 10 pounds of fat to muscle, you would be able to burn an extra 40 calories a day, which isn’t that much. No, the reason to exercise is metabolic, and you need to match that with metabolic eating.
Say you eat an apple which is all sucrose and some fiber. Half of sucrose is glucose and 76% of that burns off at the first pass while 24 % of it goes into the liver where most of it is stored as glycogen and the rest powers mitochondria for energy. Maybe a half a calorie goes through the TCA cycle which will turn into VLDL cholesterol, used to store fat. The other half is fructose of which 72% goes into the liver. The breakdown products of this fructose in the liver is far more pernicious, including uric acid which causes gout and hypertension, but more importantly high levels of VLDL and five times as much fat formation (de novo lipogenesis .) It also causes liver insulin resistance and turns off the leptin that tells your brain you have had enough food. If you take your calories in a sports drink, all of it acts like the fructose.
So what does exercise do? It burns off the fructose and glucose before it turns into VLDL and fat. It isn’t about the calorie burning, it is about the metabolic functiion.
- Exercise improves skeletal muscle’s insulin sensitivity so that sugar and corrosive insulin do not hang around in the bloodstream, but get converted into energy.
- Exercise reduces stress and lowers cortisol, which reduces obesity, especially central obesity which is the most dangerous kind.
- The de novo lipogenesis gets short circuited. The mitochondria speed up the TCA cycle to make more energy so they don’t form the citrate that gets turned into fat.
- Speeding up the TCA cycle detoxifies the fructose, improving hepatic (liver) insulin sensitivity.
- And of course it burns some calories directly
- And it builds muscles which will burn a few calories more when you are at rest.
Now Cloud seems unaware of this metabolic function, but he does point to eating after exercise as the reason people often don’t lose weight. And although he may misattribute it as a result of exercise, he is right that eating after exercise, (or worse yet drinking sports drinks), will neutralize your exercise. I know people who religiously put in two hours a day at the gym for years, and still had belly fat and insulin resistance. The reason was that they drank sports drinks which are basically vehicles for high fructose corn syrup, during and after exercise.
You need to eat before you exercise. When you eat, your insulin spikes and takes several hours to decline (2 hours for a fit person and as many as 5 for someone with insulin resistance.) When your blood insulin is elevated, you cannot biochemically burn fat or build muscle, much of which happens while you are at rest if you exercised. Peak level exercise, even for two minutes, has the immediate effect of lowering your insulin levels. So if you exercise after eating, and throw in some peak level effort for a few minutes, your workout will metabolically allow you to stop fat formation and to burn muscle.
Eating a half hour before exercise also allows you to be properly fueled for your workout. If you are properly fueled, you have both the electrolytes and the energy to work out well. You will be less likely to want to reward yourself with a Starbuck’s muffin or larger dinner.
You should still hydrate, but use water. The only exception would be for an elite athlete who just ran a marathon, lowered his glycogen stores and needs to replenish. But if we are exercising for weight loss, we haven’t used up our glycogen stores, and water is what we need to replenish fluids. The electrolytes come from the food we ate before the workout.
You do not need to put in 60-90 minutes in exercise all at once, as we believed in the 70s. You do best with a session of exercise after breakfast, including a peak effort period. Then walk around the block or do 15 minutes of exercise after your other meals. If you suffer from diabetes or insulin resistance, make sure to include two minutes of peak exercise like running up stairs or sprinting. Don’t snack on carbs without exercise after or you will bring your insulin curve up again- unsalted nuts are a better alternative. And keep the period between dinner and lunch carb free, using eggs, salmon or organic sausage and vegetables for breakfast so you have a long period where you can burn fat and build muscle. I know people who lost weight just following that last piece of advice. (If you really want your oatmeal, have it for lunch.)
To use exercise effectively, you may have to revise your patterns, especially if you are in the habit of dropping into the gym after work, before dinner. You may need to go home first and eat. If you find you don’t go back to the gym, then pack your dinner and eat before leaving work or find a healthy restaurant to frequent. Then go burn it off. Or switch your exercise sessions to the morning after breakfast.
Exercise is important to losing weight. In fact it is probably essential since fat loss is more often than not accompanied by the loss of some muscle, even without fad diets. You can keep from lowering your resting metabolism by exercise, as well as reducing