Weight-loss Strategy to Only “Eat Less, Exercise More” May be Overly Simplistic – Study

Prior research has often focused on methods for weight loss after obesity has developed. Less is known about factors linked to long-term term weight gain.

6/23/2011 --- In a series of three separate studies looking at how changes in multiple dietary and other lifestyle factors relate to long-term weight gain, Harvard School of Public Health (HSPH) researchers found that modest changes in specific foods and beverages, physical activity, TV-watching, and sleep duration were strongly linked with long-term weight gain. Changes in diet, in particular, had the strongest associations with differences in weight gain.

The study appears in the June 23, 2011, issue of the New England Journal of Medicine.

Prior research has often focused on methods for weight loss after obesity has developed. Less is known about factors linked to long-term term weight gain.

"An average adult gains about one pound per year. Because the weight gain is so gradual and occurs over many years, it has been difficult for scientists and for individuals themselves to understand the specific factors that may be responsible," said lead author Dariush Mozaffarian, associate professor in the Department of Epidemiology at HSPH and Division of Cardiovascular Medicine, Brigham and Women's Hospital (BWH), and Harvard Medical School.

The researchers evaluated changes in multiple specific lifestyle factors and weight gain every four years over 12 to 20 years of follow-up in three separate large cohorts, the Nurses' Health Study (NHS), the Nurses' Health Study II (NHS II), and the Health Professionals Follow-up Study (HPFS). The final analyses included 50,422 women in the NHS, 47,898 women in NHS II, and 22,557 men in HPFS, all of whom were free of obesity or chronic diseases at the beginning of the study. Study participants gained an average of 3.35 lb during each four-year period, which corresponded to a weight gain of 16.8 lb over the 20-year period.

When relations of lifestyle changes with weight gain were evaluated, the findings were strikingly similar in all 3 studies.

For example, the foods associated with the greatest weight gain over the 20-year study period included potato chips (for each one increased daily serving, +1.69 lb more weight gain every 4 years), other potatoes (1.28 lb), sugar-sweetened beverages (1.00 lb), unprocessed meats (0.95 lb), and processed meats (0.93 lb). Of note, several foods associated with less weight gain when their consumption was actually increased, including vegetables (−0.22 lb), whole grains (−0.37 lb), fruits (−0.49 lb), nuts (−0.57 lb) and yogurt (−0.82 lb). Evaluating all changes in diet together, participants in the lower 20% of dietary changes gained nearly 4 lbs more each 4 years than those in the top 20%  an amount equivalent to the average weight gain in the population overall.

For diet, focusing only on total calories may not be the most useful way to consume fewer calories than one expends, say the researchers. Other yardsticks, such as content of total fat, energy density, or sugars, could also be misleading. Rather, they found that eating more healthful foods and beverages focusing on overall dietary quality was most important.

The most useful dietary metrics for preventing long-term weight gain appeared to be:
•  Focus on improving carbohydrate quality by eating less liquid sugars (e.g. soda) and other sweets, as well as fewer starches (e.g. potatoes) and refined grains (e.g. white bread, white rice, breakfast cereals low in fiber, other refined carbohydrates).
•  Focus on eating more minimally processed foods (e.g. fruits, vegetables, whole grains, nuts, yogurt) and fewer highly processed foods (e.g. white breads, processed meats, sugary beverages).

Such a more healthful dietary pattern could influence long-term weight gain in many ways, including, for example, through biologic effects such as changing hunger, insulin levels, or satiety, or by improving eating behaviors related to average portion sizes and patterns of foods and beverages consumed.

"These findings underscore the importance of making wise food choices in preventing weight gain and obesity," said Frank Hu, professor of nutrition and epidemiology at HSPH and senior author of the paper. "The idea that there are no 'good' or 'bad' foods is a myth that needs to be debunked."

The results also showed that changes in physical activity and TV-viewing influenced changes in weight. Also, those who slept 6-8 hours a night gained less weight than those who slept less than 6 or more than 8 hours.

Overall, the weight-changes associated with any one lifestyle change were fairly small. However, together they added up, especially for diet. "Small dietary and other lifestyle changes can together make a big difference – for bad or good," said Mozaffarian. "This makes it easy to gain weight unintentionally, but also demonstrates the tremendous opportunity for prevention. A handful of the right lifestyle changes will go a long way."

Support for the study was provided by the National Institutes of Health and the Searle Scholars Program.

In response to the study, the American Beverage Association issued the following statement:

"Like almost all foods, sugar-sweetened beverages are a source of calories. But when it comes to weight gain, there is nothing unique about those calories, which account for only about 7 percent of the calories in the average American's diet according to a National Cancer Institute analysis of government data. This means that 93 percent of calories are coming from other sources. Importantly, the authors of this study looked at only a few foods and beverages. Several were associated with more weight gain than sugar-sweetened beverages. In fact, even every day staples like meat and potatoes were called out as significant contributors to weight gain. In addition, they found that physical inactivity, such as television viewing, contributed substantially to weight gain over time. Thus, there are many reasons for weight gain, but consuming sugar-sweetened beverages alone is not the reason.

At the end of the day, you can live a healthful lifestyle and enjoy soft drinks and other sugar-sweetened beverages in moderation. Furthermore, for consumers looking to reduce total calorie intake, our industry provides many no- and low-calorie beverage options, which research has shown can help people lose weight or maintain a healthy weight, something also reinforced in this article. This is a position supported by health organizations including the American Dietetic Association.

Importantly, our industry takes its role in being part of a comprehensive solution to reducing obesity very seriously. In support of First Lady Michelle Obama's ‘Let's Move!' campaign, America's leading beverage companies have come together in a voluntary commitment to put calorie information on the front of every bottle, can and pack they produce - and display the total calories per container on all beverages 20 fluid ounces or smaller. With the Clear on Calories initiative, the new, easy-to-understand calorie labels are designed to help consumers make the choice that is right for them and their families. These labels began appearing on some beverages last fall and are now in stores across the nation, and will appear on all brands and packages by early 2012 as committed.

This study clearly demonstrates that to maintain a healthy weight, what matters most is balancing calories consumed from all foods and beverages with those expended through physical activity."

"Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men," Dariush Mozaffarian, Tao Hao, Eric B. Rimm, Walter C. Willett, Frank B. Hu, NEJM, June 23, 2011.