Even as Americans have been gaining weight, they have cut their average fat intake from 36 to 34 percent of their total diets in the past 15 years．And indeed, cutting fat to control or lose weight makes sense．Fat has nine calories(卡路里)per gram．Protein and carbohydrates(碳水化合物)have just four．Moreover, the body uses fewer calories to metabolize(新陈代谢)fat than it does to metabolize other foods．Compared with protein and carbohydrates－which break down into amino acids(氨基酸)and simple sugars, separately, and can be used to strengthen and energize the body－dietary fat is more easily changed to body fat．Therefore, it’s more likely to stay on the middle parts of a body．
But cutting fat from your diet doesn’t necessarily mean your body won’t store fat．For example, between nonfat and regular cookies, there’s only slight difference in calories because manufacturers make up for the loss of fat by adding sugar．Low-fat crackers, soups and dressings can also be just as high in calories as richer ones．No matter where the calories come from, overeating will still cause weight again．The calories from fat just do it a little quicker．A Wisconsin computer programmer who decided with a diet coach to eat only 40 grams of fat a day learned the lesson firsthand．He wasn’t losing weight．Then he showed his food diary to his coach and suggested he’d been eating half a pound of jelly beans a day．“They don’t have any fat,” he explains．But they had enough sugar to keep him from losing an ounce．
Nonfat foods become add-on foods．When we add them to our diet, we actually increase the number of calories we eat per day and gain weight．That was shown in a Pennsylvania State University study．For breakfast, Prof．Barbara Rolls gave two groups of women yogurt(酸奶)that contained exactly the same amount of calories．One group’s yogurt label said “high fat”－the other, “low fat.” The “low fat” yogurt group ate much more calories later in the day than the other group．“People think they’ve saved fat and can indulge(放纵)themselves later in the day with no harmful results,” says Richard Mattes, a nutrition researcher at Purdue University．“But when they do that, they don’t remove the bad effect precisely, and they often end up overdoing it．”
(1)
Americans are still gaining weight, because ________．
[ ]
A．
they eat too much fat．
B．
they overeat．
C．
they eat low-fat crackers, soups and dressings．
D．
they eat sugar．
(2)
What lesson did the computer programmer learn?
[ ]
A．
Overeating will cause weight gain．
B．
He can eat half a pound of jelly beans a day．
C．
He didn’t eat any fat．
D．
His coach gave him a lecture．
(3)
Prof．Barbara’s experiment proved that ________．
[ ]
A．
two groups ate the same amount of calories
B．
two groups ate the same amount of yogurt
C．
the“low fat”yogurt group ate much more calories later in the day than the other group
D．
people increase the number of calories they eat per day and gain weight
(4)
According to the author, ________ has less calories．
