Frequent nibbling may be better for a person's cholesterol level than eating three square meals a day, Canadian researchers suggest in a study published today in the New England Journal of Medicine.
Levels of "bad" LDL cholesterol were 13.5% lower when study subjects ate small amounts of food 17 times a day than when they ate the same food but in three conventional meals, the University of Toronto scientists found. Total cholesterol in their blood, a combination of LDL and a beneficial form, called HDL, declined to 8.5% lower than on the three-meal plan.
The results indicate that a person trying to cut cholesterol and the risk of heart disease could maximize the effects of a low-fat diet by also changing to small, frequent meals, said Dr. David J.A. Jenkins, professor of medicine and nutritional science, and chief author of the study.
"In terms of the average man and woman, they will never go out and eat 17 meals a day," Jenkins said, "but we are saying that there seems to be some advantage to spreading the intake load during the day."
If the idea sounds familiar, it is a basic tenet in dietary advice given to diabetics, and also has shown up in the last decade among a group of Americans the food industry refers to as "grazers."
Grazers nibble their way through the day, sampling many different types of foods in small portions. The rise in appetizers on restaurant menus is one result, restaurant industry spokesmen say.
In addition, in the 1960s a series of research studies compared the effects of nibbling and gorging on cholesterol levels in the blood. The studies concluded that nibbling was better, and gorging was bad--but nibbling was abandoned as a health strategy because overeaters who were urged to adopt nibbling tended to overeat several times a day instead of three times a day.
Nonetheless, Jenkins and his colleagues suggest that the strategy may be useful as a cholesterol control strategy added to other dietary changes, if the patient's preferred eating pattern is already toward nibbling.
"There are some people who can nibble or who can train themselves to nibble, and they would get some material advantage from this," Jenkins said.
In addition to confirming the earlier studies' results, the Toronto team suggests the biochemical mechanism for why nibbling suppresses cholesterol levels: the maintenance of a steady level of insulin in the body is responsible for this effect.
This is because when a large amount of food is eaten, the pancreas responds by releasing a large amount of insulin, a hormone that is essential for the body to use sugar. The insulin stimulates the body to produce an enzyme that in turn causes the liver to produce cholesterol and dump it into the blood, they report. Excess insulin also has been shown to stimulate changes in the arterial walls that promote formation of fatty plaques, leading to coronary heart disease.
The Toronto researchers put seven men--ages 31 to 51 and with an average total cholesterol level of 204 mg per deciliter of blood--onto a 33% fat diet. This proportion is similar to that being advocated as healthy by various nutritional experts. The diet gave roughly 2,500 calories a day.
The federal government's cholesterol education program defines total cholesterol levels below 200 as desirable, 200-239 as borderline high-risk and 240 or above as at high-risk of cardiovascular disease.
Each man spent two weeks on the nibbling diet, eating every hour during the day, and another two weeks eating the same types and total amounts of food, but in three normal meals. The test periods were separated by two weeks in which the subjects ate their normal diets.
During the nibbling phase, a pocket timer reminded the subjects to eat their small snacks prepackaged by the researchers--for instance a half-slice of bread, a bare smear of margarine and half of a banana. During a dinner-hour splurge, subjects had three ounces each of broccoli, cauliflower and zucchini.
With nibbling, total cholesterol levels fell from an average of 204 to 172. They also fell on the three-meal diet, to 189. Total cholesterol was 8.5% lower on the nibbling diet than on the three-meal one.
The average levels of LDL, or bad cholesterol, fell from 127 to 105 on the nibbling diet, 13.5% lower than on the three-meal diet. LDL levels on the three-meal diet did not change significantly.
LDL levels below 130 are considered desirable and above 160 high-risk. Since LDL is a major cholesterol carrier released into the blood by the liver, it is considered the major indicator of potential problems.
Jenkins said reactions to the diet varied, depending on the person's normal eating habits.
"Some individuals are nibblers, and some individuals are meal eaters," he said. "Meal eaters detested the nibbling because they never got a meal, and they hated eating all the time. The nibblers found being constricted to three meals without snacks was rather unpleasant, and they found themselves getting particularly hungry between meals."
Dieter Kramsch, professor of research medicine in USC's Atherosclerosis Research Institute, said the Toronto study is noteworthy.
Jenkins gives this advice to Americans who want to apply the Toronto research in their daily lives: "They should be very wary of the quick cup of coffee and cigarette in the morning, further coffee and a Danish at lunch and the entire balance of one day's intake at dinner time--which is unfortunately a habit of many tired people when they get home from work," he said.