The body's reaction to summer sun is identical to its response to fever, according to nutrition consultant Dr. Joannie Dobbs.

"When you eat, your metabolism increases. The body has to work harder to get rid of the excess heat. When you have a fever, you don't feel like eating because the body is doing what it can to keep your temperature down."

Trish Britten, a UH extension specialist in food and nutrition, calls the rising metabolism the "thermic effect of food."

"Usually blood flows right beneath the skin. When you eat, blood is directed to the stomach and digestive area, so the body is not able to radiate heat."

To regulate body temperature, she said, appetite is suppressed.

Reduced activity during summer months might also explain our need for less fuel. However, if our activity level remains the same and we seem to be getting by on less food, it could just mean that we're overeating at other times of the year.

"Our bodies tell us if we need more energy," Dobbs said. "But humans eat more than they need. We eat for taste. We could be eating out of habit, even if appetite is not there."

The body's main hot weather needs are water and potassium. Sources of potassium include commercial sports drinks, bananas, orange juice, chili peppers, milk, green peppers and strawberries.

On a cellular level, the body knows what it needs to cool down, but we cooperate reluctantly, if at all.

Rather than thinking salad and soft drink for lunch, diners tend to order the plate lunch or burger they're accustomed to. Those seeking respite from the heat reach for a cold beer or a cold treat such as ice cream, but Dobbs says alcohol is more likely to cause dehydration and suggests people would be better off choosing sorbet instead of fat-filled ice cream.

"When people choose ice cream, they're going for it because it's cold. But fat slows down the blood system even more. So instead of feeling more energy, the body has to work on digesting fat, so they feel sluggish.

With a post doctorate degree in zoology, Dobbs spent five years in Africa studying vultures, and in observing other animals, she said, "Animals have a real drive for water."

This need also pertains to humans, but is not always addressed. The elderly especially may suffer from an impaired thirst mechanism, and Dobbs said by the time one feels thirsty, one is already suffering an early stage of dehydration.

"One should never feel thirsty. You need to drink eight glasses of water a day, and during the summer you need even more."

"In the elderly whose thirst mechanism is not very good, they're likely to stop drinking, and when you stop drinking, you eat even less," she said. "It's a vicious cycle and not a good survival mode."