Philip J. Goscienski, M.D.
Diet: A method for training the body to gain weight and to keep it on.
That definition of a diet contains both truth and humor. Most persons who try to lose weight by cutting way back on calories regain the lost pounds in a year or two and often pack on a few more. You may have noticed that some recent TV ads and book promotions promise that you will not only lose weight but that you will keep it off, with emphasis on "keep it off."
We are hard-wired to survive in the face of food scarcity. When calorie intake goes down, nature takes over and calls in the defense. It's logical to assume that we'll immediately start using up stored fat during a period of starvation but that's not what happens.
The first thing to go is the glycogen that we have accumulated in the liver and muscles when food was plentiful. Known as animal starch, glycogen breaks down quickly into blood sugar and provides immediate energy. Most of us have about a day's worth of this stored energy. When it's gone and there are few calories coming in, ordinary activity leaves us tired and sluggish. Ask any dieter.
The brain demands a hefty share of energy. About 25 percent of the heart's output of blood goes to the brain, bringing oxygen and sugar (glucose). Lowering blood sugar leads to fuzzy thinking, slow reaction times and irritability. Ask anyone who has lived with a dieter!
A low-calorie, low-carbohydrate (Atkins-type) diet forces the body to go elsewhere in its search for glucose and it doesn't come from fat! Protein is the next source after glycogen. Gluconeogenesis is literally the "formation of new sugar" and it's a costly mechanism. The largest mass of protein in the body is the muscle mass that we need to move, lift and carry in order to get through our daily chores. It's also where nearly half of the diet-induced weight loss comes from (the rest comes from water and fat) and it doesn't come back when the diet is over. A vigorous program of exercise during a diet helps to reduce the loss of muscle but that's not easy when you're starving yourself.
Eventually the body starts peeling off fat by breaking it down into small energy-yielding molecules. These ketones don't deserve the bad rap that some give them, except for the characteristic bad breath that marks the low-carb dieter.
Rapid weight loss often leads to gallstone formation and the subsequent need for gallbladder surgery. That's a high price to pay for losing weight that will come back anyway.
By losing weight slowly and being physically active (yeah — that means exercise!) it's possible to avoid these problems. Most of us accumulate only a pound or two a year on our way to overweight or obesity. It doesn't make much sense to shed it all in a matter of months. If you trim only about 300 calories (10 percent of the average intake) from your meals every day and burn off about 200 with a brisk 45-minute walk almost every day you'll lose about one pound per week, and it will be fat, not muscle.
Philip J. Goscienski, M.D. is the author of Health Secrets of the Stone Age, Better Life Publishers 2005. Contact him at firstname.lastname@example.org.