WEDNESDAY, June 22, 2011 (HealthDay News) -- The edict to eat less and exercise more is far from far-reaching, as a new analysis points to the increased consumption of potato chips, French fries, sugary sodas and red meat as a major cause of weight gain in people across the United States.
Inadequate changes in lifestyle factors such as television watching, exercise and sleep were also linked to gradual but relentless weight gain across the board.
Data from three separate studies following more than 120,000 healthy, non-obese American women and men for up to 20 years found that participants gained an average of 3.35 pounds within each four-year period -- totaling more than 16 pounds over two decades.
The unrelenting weight gain was tied most strongly to eating potatoes, sugar-sweetened beverages, red and processed meats and refined grains such as white flour.
"This is the obesity epidemic before our eyes," said study author Dr. Dariush Mozaffarian, an associate professor in the department of epidemiology at Harvard School of Public Health and the division of cardiovascular medicine at Brigham and Women's Hospital and Harvard Medical School. "It's not a small segment of the population gaining an enormous amount of weight quickly; it's everyone gaining weight slowly."
"I was surprised how consistent the results were, down to the size of the effect and direction of the effect," he said.
The study is published in the June 23 issue of the New England Journal of Medicine.
Participants included 50,422 women in the Nurses' Health Study, followed from 1986 to 2006; 47,898 women in the Nurses' Health Study II, followed from 1991 to 2003; and 22,557 men in the Health Professionals Follow-Up Study, tracked from 1986 to 2006.
The researchers assessed independent relationships between changes in lifestyle behaviors and weight changes within four-year periods, also finding that those doing more physical activity translated into 1.76 fewer pounds gained during each time period.
Participants who slept less than six hours or more than eight hours per night also gained more within each study period, as did those who watched more television (an average of 0.31 pounds for every hour of TV watched per day).
And fast food addicts, beware: Each increased daily serving of potato chips alone was associated with a 1.69 pound-weight gain every four years. Other foods most strongly associated with weight gain every four years were potatoes, including fries (a 1.28-pound gain), sugar-sweetened beverages (1-pound gain), unprocessed red meats (0.95-pound gain), and processed meats (0.93-pound gain).
Alcohol use was also associated with about a 0.41-pound gain per drink per day.
"These are the kinds of studies that help justify the basis for the dietary guidelines we've been trying to promote for years," said Lona Sandon, an assistant professor of clinical nutrition at University of Texas Southwestern in Dallas. "Really, there is a synergy of these lifestyle behaviors. It's not about a single food, or a single dietary technique, or exercising until your head falls off."
"These aren't extreme measures, either -- just sitting in front of the TV a little less," Sandon added. "It's important to get across that it's the whole package, not any one thing."
Foods associated with stable weight or less weight gain included vegetables, whole grains, fruits, nuts, yogurt and low-fat dairy food. The findings were broadly consistent with cross-sectional national trends regarding diet and obesity, the authors said, noting that the average calorie intake in the United States increased 22 percent among women and 10 percent among men between 1971 and 2004.
"Our take-home message is what you eat affects how much you eat," Mozaffarian said. "It's not just a blanket message about reducing everything. Each individual lifestyle factor has a pretty small effect by itself, but the combined effect can explain that gradual weight gain."
Sandon said weight-reduction programs such as Weight Watchers work for many because they focus on changing behavior over the long term instead of focusing on quick fixes.
"I don't think people are unaware of what they should be doing, but how do we change that motivation so we change behavior on a daily basis?" she said. "It's a process."
The U.S. Centers for Disease Control and Prevention has more information on lifestyle changes to boost heart health.