It’s no secret that Americans are fatter today than ever before, and not just those unlucky people who are genetically inclined to gain weight or have been overweight all their lives. Many who were lean as young adults have put on lots of unhealthy pounds as they pass into middle age and beyond.
It’s also no secret that the long-recommended advice to eat less and exercise more has done little to curb the inexorable rise in weight. No one likes to feel deprived or leave the table hungry, and the notion that one generally must eat less to control body weight really doesn’t cut it for the typical American.
¶ So the newest findings on what specific foods people should eat less often — and more importantly, more often — to keep from gaining pounds as they age should be of great interest to tens of millions of Americans.
¶ The new research, by five nutrition and public health experts at Harvard University, is by far the most detailed long-term analysis of the factors that influence weight gain, involving 120,877 well-educated men and women who were healthy and not obese at the start of the study. In addition to diet, it has important things to say about exercise, sleep, television watching, smoking and alcohol intake.
¶ The study participants — nurses, doctors, dentists and veterinarians in the Nurses’ Health Study, Nurses’ Health Study II and the Health Professionals Follow-up Study — were followed for 12 to 20 years. Every two years, they completed very detailed questionnaires about their eating and other habits and current weight. The fascinating results were published in June in The New England Journal of Medicine.
¶ The analysis examined how an array of factors influenced weight gain or loss during each four-year period of the study. The average participant gained 3.35 pounds every four years, for a total weight gain of 16.8 pounds in 20 years.
¶ “This study shows that conventional wisdom — to eat everything in moderation, eat fewer calories and avoid fatty foods — isn’t the best approach,” Dr. Dariush Mozaffarian, a cardiologist and epidemiologist at the Harvard School of Public Health and lead author of the study, said in an interview. “What you eat makes quite a difference. Just counting calories won’t matter much unless you look at the kinds of calories you’re eating.”
¶ Dr. Frank B. Hu, a nutrition expert at the Harvard School of Public Health and a co-author of the new analysis, said: “In the past, too much emphasis has been put on single factors in the diet. But looking for a magic bullet hasn’t solved the problem of obesity.”
¶ Also untrue, Dr. Mozaffarian said, is the food industry’s claim that there’s no such thing as a bad food.
¶ “There are good foods and bad foods, and the advice should be to eat the good foods more and the bad foods less,” he said. “The notion that it’s O.K. to eat everything in moderation is just an excuse to eat whatever you want.”
¶ The study showed that physical activity had the expected benefits for weight control. Those who exercised less over the course of the study tended to gain weight, while those who increased their activity didn’t. Those with the greatest increase in physical activity gained 1.76 fewer pounds than the rest of the participants within each four-year period.
¶ But the researchers found that the kinds of foods people ate had a larger effect over all than changes in physical activity.
¶ “Both physical activity and diet are important to weight control, but if you are fairly active and ignore diet, you can still gain weight,” said Dr. Walter Willett, chairman of the nutrition department at the Harvard School of Public Health and a co-author of the study.
¶ As Dr. Mozaffarian observed, “Physical activity in the United States is poor, but diet is even worse.”
¶ Little Things Mean a Lot
¶ People don’t become overweight overnight.
¶ Rather, the pounds creep up slowly, often unnoticed, until one day nothing in the closet fits the way it used to.
¶ Even more important than its effect on looks and wardrobe, this gradual weight gain harms health. At least six prior studies have found that rising weight increases the risk in women of heart disease, diabetes, stroke and breast cancer, and the risk in men of heart disease, diabetes and colon cancer.
¶ The beauty of the new study is its ability to show, based on real-life experience, how small changes in eating, exercise and other habits can result in large changes in body weight over the years.
¶ On average, study participants gained a pound a year, which added up to 20 pounds in 20 years. Some gained much more, about four pounds a year, while a few managed to stay the same or even lose weight.
¶ Participants who were overweight at the study’s start tended to gain the most weight, which seriously raised their risk of obesity-related diseases, Dr. Hu said. “People who are already overweight have to be particularly careful about what they eat,” he said.
¶ The foods that contributed to the greatest weight gain were not surprising. French fries led the list: Increased consumption of this food alone was linked to an average weight gain of 3.4 pounds in each four-year period. Other important contributors were potato chips (1.7 pounds), sugar-sweetened drinks (1 pound), red meats and processed meats (0.95 and 0.93 pound, respectively), other forms of potatoes (0.57 pound), sweets and desserts (0.41 pound), refined grains (0.39 pound), other fried foods (0.32 pound), 100-percent fruit juice (0.31 pound) and butter (0.3 pound).