The skinny on fat The skinny on fat (December 10, 2004)

Q: What's the lowdown on the popular low-carb diets? A: Not all carbohydrates are created equal, but they are all sugars. All of the calories we eat come from carbohydrates, proteins or fats. We need all three in our diets to survive. We also need vitamins, minerals and fluids. The trick is getting the proper mix and, at the same time, limiting our total caloric intake so we don't get fat.

There are "good" and "bad" carbs. Vegetables and fruits are carbs, which surprises a lot of patients. All starches are carbs (pasta, potatoes, bread, rice and crackers) as are refined sugars (including cakes, cookies and candy). Alcoholic beverages and fruit juices are also carbs.

Carbs stimulate insulin secretion, which regulates our blood sugar levels. Good carbs maintain your blood sugar levels more evenly. This prevents spikes in insulin which make you feel hungry. Most experts agree that carbohydrates should be the major source of our caloric intake, followed by protein, and then fat. Healthy, low-carb diets emphasize vegetables and fruits and limit sweets, starches and alcohol.

The South Beach Diet is the best low-carb diet on the scene. The menus are appealing and heart-healthy. The Zone diet also makes sense but it's not as easy to properly prepare and balance each meal and snack. Though the Atkin's Diet was among the first to gain popularity, it doesn't limit fat intake or differentiate between the types of fat. It is not a long-term, heart-healthy diet.
Q: What's a "trans" fat? A: Fats are divided into two groups. Saturated fats are solid at room temperature (like the fat in meat). They increase bad cholesterol and should be avoided. Unsaturated or monosaturated fats are oils, including olive and canola or the oil in nuts.

Trans fats are created by the partial hydrogenation of vegetable oils. They are the worst kind of fat, along with saturated fat, with roughly twice the number of calories per ounce compared to proteins and carbs.

Trans fats are put into food to increase shelf life, but they decrease health. They cause significant lowering of good cholesterol and an increase in bad cholesterol, which promotes arteriosclerosis and cardiovascular disease.
Q: I'm tired of losing weight only to gain it again. Which diet really works? A: Opt for moderate changes that are likely to be permanent, rather than short-lived drastic weight loss efforts. Sensible eating and exercise is the perfect recipe. Before launching any new diet, talk to your physician about options that are best for you, especially if you have any special health conditions.
Responses provided by Stuart Markovitz, M.D., who practices internal medicine at Camino Medical Group's Castro Commons Clinic in Mountain View.
Have a medical question? E-mail it to Cynthia Greaves at greavec@caminomedical.org.

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