DEAR DR. BLONZ: In my 20s and 30s, I was able to maintain a reasonable weight with diet and exercise. Now, at 43, I have maintained my activity, but have been gradually gaining weight. I now find myself about 15 pounds overweight. I have researched diets and am considering going very low-carbohydrate, but I want to know how this diet is supposed to work and whether it's worth it. -- F.T., Chicago
DEAR F.T.: When you eat a diet that is very low in carbohydrates (under 20 grams a day), you have threatened your body's access to glucose. A chronic shortage of available glucose creates the situation in which your get-up-and-go energy will have, in effect, gotten up and gone.
The fat stored in our body is our major energy reserve, but the body needs small amounts of glucose to help it burn the fat correctly. The incomplete combustion of fats produces ketone bodies, and these can be toxic if allowed to accumulate. The body starts to eliminate them through the urine. The resulting condition, called ketosis, also occurs with uncontrolled diabetes; there, the body is unable to produce the insulin needed to let glucose into the energy-producing (fat-burning) cells of the body.
Certain tissues -- including the red blood cells, the kidney medulla, the lens of the eye and even the brain -- rely on glucose as a primary fuel. When there isn't enough glucose, the body begins to scavenge around for potential sources among its own tissues. The liver has glycogen, a source of stored carbohydrate, and there is a small amount in the muscles, but the amount stored is small in relation to total bodily needs.
Protein can be used, because some of its amino acids can be turned into glucose. The muscles represent the body's largest reserve of protein, and like all protein tissues, they are about 80 percent water by weight. When the body begins to break down muscle tissue to get amino acids to turn into glucose, the water portion of muscle tissue gets released and eliminated. Like magic, the numbers on the scale begin to go down -- but it is water weight, not excess body fat, you are losing. This type of lost water weight is quickly regained once carbohydrates are back on the plate.
The bottom line is that a low/no-carbohydrate diet is a questionable way to lose weight. And besides, who wants to live life without carbohydrates?
It is important to accept that it's not unusual to gain weight as we pass through our 30s, 40s and on up. It's a natural side effect of an age-related slowdown in our metabolic rate, coupled with a trend toward less physical activity as we age. While the former is beyond our control, we can definitely do something about the latter.
A good strategy is to avoid quick-fix fad diets and strive to be the healthiest person you can be. I am certainly impressed by your attempts to stay active, and I hope you are able to keep it up regardless of which dietary path you choose. I wish you the best.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.