Q: Can you tell me when an individual is considered a candidate for surgical treatment of obesity?

A: A task force of the American Society for Clinical Nutrition chaired by Dr. T.B. Van Itallie recently issued a set of guidelines for the evaluation, selection, care and follow-up of candidates for surgical treatment of obesity. Those guidelines recommend that the measure be limited to individuals whose body weight exceeds their average desirable weight by 100 pounds or by 100 percent, or who have one or more serious medical conditions related to severe obesity that has not responded to other treatment.

The persons should have a history of repeated failure to lose weight by nonsurgical approaches. They should have been within the weight criteria for three to five years. And they must be able to tolerate the trauma of surgery and anesthesia, with special attention directed toward disqualifying individuals with serious medical conditions until they had been treated successfully.

The guidelines also said that individuals should not be accepted for surgery without a thorough examination addressing problems that might increase surgical risk or jeopardize successful outcome. Alcohol, drug addiction and other mental-health problems that would influence patient cooperation during follow-up should be considered as possible reasons not to perform surgery. The task force specified guidelines for hospitals doing the surgery, including recommendations that doctors inform patients about all aspects of the procedure.

Finally, they recommended a National Registry to collect and evaluate results of different types of obesity surgery.

Q: I have been advised by my pediatrician to give my young son an iron supplement. But recently I read that too much iron can interfere with zinc absorption. I began to wonder: Are supplements really safe for young children?

A: According to the latest findings of a group of researchers led by Dr. Peter Dallman from the University of California at San Francisco, iron supplements do not compromise zinc status, at least when given apart from meals, as they were in that study.

The investigators evaluated the iron status as well as the serum zinc and copper levels of a group of 291 1-year-olds, who were then divided into two groups. Half were given an iron supplement to be taken a half-hour before breakfast and the rest a placebo, or sugar pill. At the end of three months, blood tests were repeated. While some measures of iron status improved as expected, serum zinc and copper levels did not change.

The researchers offer several explanations for their findings, which seem to differ from previous reports of adverse effects of iron supplements on zinc absorption. First, in one earlier study in which iron was found to affect zinc absorption negatively, subjects were given doses of both minerals at the same time. Indeed, in most studies of the suppression of absorption of one mineral or another, both are given at the same time. Immediate changes in serum-zinc levels may not be reflective of a consistent effect on zinc retention.

In adults, it has been shown that while zinc absorption is depressed under fasting conditions, this does not occur if the two minerals are given with a meal, or when zinc is given in a form where it is tied to a so-called "dietary ligand," or binding agent. (This phenomenon has not yet been studied in infants.)

Thus the question of whether iron supplements taken along with meals or giving iron without other minerals could jeopardize zinc nutrition, especially in infants who are not well nourished, remains to be investigated. This study does provide reassurance that a common mode of iron supplementation in infants does not compromise either their zinc or copper nutrition.

Q: For the past several years I have made a serious effort to reduce my fat intake and eat less saturated fat. Yesterday, however, I noticed that the vitamin supplement I was taking contained vitamin A palmitate. I am aware that palm oil is highly saturated and carefully avoid foods where it is used. But am I inadvertently getting it in my vitamins?

A: The palmitate with which the vitamin A is combined comes from a so-called long-chain fatty acid (that is, it contains 12 or more carbon atoms -- in this case, 16). It is just one of the mixture of fats found in palm oil, and it is highly saturated. But there is no need to worry, since the smidgen you get tied to vitamin A in a multivitamin capsule is too small to be of any consequence.