Losing weight and achieving the rippled "six-pack" stomach has become a national obsession. Although a year-round obsession for some, for many of us this focus on leanness intensifies with summer weather and the opportunity for more beach time.

For those cutting calories to control their weight, we often hear the lament that they lose all will power after a few weeks and food cravings become overwhelming. Is this just due to a lack of will power? Or, are there real biological consequences to not meeting calorie and nutrient requirements?

Question: What is a food craving?

Answer: Depending on the area of research, there are many definitions. However, for this article, we will refer to a food craving as the intense drive to consume a particular food or beverage or a food with a particular taste or texture.

Q: Are food cravings normal?

A: Although it is common for some people to feel their food cravings are abnormal and to even feel guilty about them, cravings are common and natural. In fact, many cravings may have good biological reasons that relate to basic survival instincts to meet nutritional needs.

Q: What are the most common cravings?

A: Research indicates that men generally have fewer cravings than women. Men have a tendency to crave full meals rather than specific foods. For women, studies indicate that chocolate is the most commonly craved food, with a basic craving for something sweet not far behind. Chewing ice is another craving that is primarily seen in women who are iron deficient, with or without anemia. Another common craving, documented mostly by animal studies, is an increase in the "sweet tooth" when calorie and especially protein consumption are inadequate.

Q: What triggers food cravings?

A: There are many potential causes such as hunger and boredom. A monotonous diet with little food variation or an eating style that has made certain foods taboo are commonly associated with increased food cravings.

Possibly the most basic trigger is restricting calories. Researchers found that a 1,200-calorie diet in normal-weight individuals, for just two weeks, triggered a predictable preoccupation with food and eating. However, diet-related cravings can be more specific. For example, when carbohydrates are restricted, it is common to crave "carbs" and to overeat them when they are reintroduced into the diet.

Q: Is there any way to lose weight without triggering these crazy food urges?

A: Some individuals seem to be able to fast and lose weight without food cravings — at least initially. However, as calorie restriction continues, there are multiple metabolic changes that can have long-term consequences. For example, if protein intake is inadequate, muscle tissue can be lost instead of fat. Loss of muscle lowers the body’s overall calorie needs, leaving the dieter in a state that favors conservation of body fat and promotes accumulation of more fat after the diet is over.

The combination of low calories and low protein also can increase bone loss and the long-term risk of osteoporosis.

To prevent excess calorie-cutting and reduce the risk of cravings, what works best is a combination of modest calorie reduction, maintaining a good protein intake and engaging in some form of physical activity. Staying well hydrated also can be helpful, but excessive water consumption can be counterproductive.

Alan Titchenal, Ph.D., C.N.S., and Joannie Dobbs, Ph.D., C.N.S., are nutritionists in the Department of Human Nutrition, Food and Animal Sciences, College of Tropical Agriculture and Human Resources, University of Hawaii-Manoa. Dobbs also works with University Health Services.