Medical memo

A little at a time: Eating and exercising in bits and pieces

It's hard to ignore advice from experts. For years, nutritionists (and mothers) have made three square meals the gold standard for healthy eating. Likewise, physiologists (and coaches) have advocated regular exercise for optimal fitness. But in today's busy world, it can be hard for a guy to sit down for three meals or to stay moving for 30 straight minutes. Is there another way?

Possibly. New research suggests that frequent small meals can be nutritionally sound and that frequent short periods of exercise can add up to fitness and health. It may not be better, but it is different.

First, eating — or grazing, as the pattern is called. Over the years, scientists have observed that when animals are allowed to nibble, they have lower cholesterol levels than when they are encouraged to gorge, even though their total food consumption is the same. Experiments on humans have produced similar findings, but the studies were brief and involved small numbers of volunteers who were given test meals in a research setting. Now, though, a study from Great Britain suggests that people in the real world may get similar results. More than 14,500 individuals between the ages of 45 and 75 volunteered for this study. Each filled out a detailed questionnaire that asked for information on the frequency of eating, the type and amounts of the foods consumed, exercise patterns, and other health habits. Each volunteer gave a blood specimen, and each was weighed and measured.

When the scientists tallied the results, they found that the people who ate more frequently took in more calories. Surprisingly, though, they also had lower cholesterol levels. The difference was relatively slight, about 5%, but it was consistent and significant, even after exercise, body weight, smoking, and other factors were taken into account. In all, the researchers found that people who eat six or more times a day have cholesterol levels that should reduce their cardiac risk by 10%–20% compared with people who eat once or twice a day. And male (but not female) "grazers" were also leaner than "gorgers," even though they took in more calories.

The French have special dietary preferences, but a 2002 study of 330 men found that those who eat more frequently have less body fat than those who eat less frequently. For example, the Frenchmen who ate one or two meals a day had an average body mass index (BMI) of 26.2 and an average waist-to-hip ratio (WHR) of 0.95, putting them in the overweight range. In contrast, the men who ate five times a day were leaner, with an average BMI of 24.5 (normal) and a WHR of 0.93. Finally, a more recent study of 499 Massachusetts residents suggests that grazing has similar effects on both sides of the Atlantic. People who ate four or more times a day were 45% less likely to be obese than those who ate three or fewer times a day.

You may be able to divide your meals into snacks, but should you split your walk into segments? To answer the question, the Harvard Alumni Study investigated 7,307 men with an average age of 66. Each volunteer reported the frequency, intensity, and duration of his exercise, and the researchers evaluated the cardiac risk factors of each man. None of the men had coronary artery disease when they enrolled in the study. After five years, though, 482 men had been diagnosed with heart disease. As in many earlier studies, the men who were most active enjoyed the lowest incidence of heart trouble, even after other risk factors were taken into account. But the frequency of exercise didn't influence protection one way or the other. The men who got their exercise in small chunks did just as well as those who exercised in a few longer workouts, as long as they ended up burning the same number of calories in the course of a week.

Is there something special about the mature men of Harvard? The Alumni Office would say yes, but when it comes to exercise, the answer is no. A study of young female college students in Wisconsin found that daily exercise was equally beneficial whether it occurred in a single 30-minute session, two 15-minute sessions, or three 10-minute sessions. And in each case the benefits were substantial: In 12 weeks, the women who exercised three times a day averaged nearly 10 pounds of weight loss and also improved their cardiopulmonary fitness scores. In addition, British scientists reported similar results, finding that three 10-minute walks a day and one 30-minute daily walk had equally good effects on blood cholesterol levels and stress and mental tension. Finally, researchers in both the United States and England have found that bouts of exercise throughout the day helped clear the fatty substances that enter the blood after eating as well as 30 minutes of continuous exercise.

What does it all mean for you? To be healthy, you still have to eat right and exercise regularly. But the research shows that what you eat is more important than when you eat it, and what you do is more important than how you do it. Still, you have to follow the rules. If you snack on the wrong food or pack in too many calories, you'll lose ground. And if you don't cover enough ground with your exercise "snacks," you won't get the full benefit of physical activity.

Even if the traditional wisdom of your mother and your coach has been updated, your math teacher prevails: The whole is still equal to the sum of its parts.