Study Title:

Snacking Reduces Weight Loss Effectiveness

Study Abstract

Snacking may play a role in weight control. The associations of timing and frequency of snacking with observed weight change and nutrient intake were assessed in an ancillary study to a 12-month randomized controlled trial in Seattle, WA. Overweight-to-obese postmenopausal women (n=123) enrolled in the two dietary weight-loss arms from 2007 to 2008 with complete data at 12 months were included in these analyses. Generalized linear models were used to test the associations between snacking and weight loss (percent) and nutrient intake at the 12-month time point. Participants were, on average, 58 years old and mainly non-Hispanic white (84%). Ninety-seven percent reported one or more snacks per day. Weight loss (percent) was significantly lower among mid-morning (10:30 am to 11:29 am) snackers (7.0%, 95% confidence interval: 4.3 to 9.7) compared to non–mid-morning snackers (11.4%, 95% confidence interval: 10.2 to 12.6; P=0.005). A higher proportion of mid-morning snackers reported more than one snack per day (95.7%), compared to afternoon (82.8%) and evening (80.6%) snackers, although differences were not statistically significant (P>0.005). Women who reported two or more snacks per day vs one or no snacks per day had higher fiber intake (P=0.027). Afternoon snackers had higher fruit and vegetable intake compared to non–afternoon-snackers (P=0.035). These results suggest that snack meals can be a source for additional fruits, vegetables, and fiber-rich foods; however, snacking patterns might also reflect unhealthy eating habits and impede weight-loss progress. Future dietary weight-loss interventions should evaluate the effects of timing, frequency, and quality of snacks on weight loss.

From press release:

Women dieters who grab a snack between breakfast and lunch lose less weight compared to those who abstain from a mid-morning snack, according to a study led by researchers at Fred Hutchinson Cancer Research Center.

The results of this randomized trial, led by Anne McTiernan, M.D., Ph.D., a member of the Hutchinson Center's Public Health Sciences Division and director of its Prevention Center, will be published in the December issue of the Journal of the American Dietetic Association.

In the course of the year-long study, the researchers found that mid-morning snackers lost an average of 7 percent of their total body weight while those who ate a healthy breakfast but did not snack before lunch lost more than 11 percent of their body weight. For the study, a snack was defined as any food or drink that was consumed between main meals.

"We think this finding may not relate necessarily to the time of day one snacks, but rather to the short interval between breakfast and lunch. Mid-morning snacking therefore might be a reflection of recreational or mindless eating habits rather than eating to satisfy true hunger," said McTiernan, the corresponding author of the paper.

While snacking too close to a main meal may be detrimental to weight loss, waiting too long between meals also may sabotage dieting efforts, she said. "Snacking could be part of a dieter's toolkit if they're eating in response to true hunger. Individuals should determine if they experience long intervals -- such as more than five hours -- between meals. Adding a snack might help people deal better with hunger and ultimately help them to make more sound choices at their next meal."

The study also revealed that women who reported eating more than two snacks a day had higher fiber intake than those who snacked less frequently, and afternoon nibblers ate more fruits and vegetables compared to women who didn't snack between lunch and dinner.

The ancillary study, part of a larger randomized clinical trial designed to test the effects of nutrition and exercise on breast cancer risk, involved 123 overweight-to-obese postmenopausal Seattle-area women, ages 50 to 75, who were randomly assigned to either a diet-alone intervention (goal: 1,200 to 2,000 calories a day, depending on starting weight, and fewer than 30 percent of daily calories from fat), or diet plus exercise (same calorie and fat restrictions plus 45 minutes of moderate-to-vigorous exercise per day, five days a week). While the women received nutrition counseling they were not given any specific instructions or recommendations about snacking behavior.

At the end of the study the women were asked to record the time, type and frequency of meals consumed on a normal day. Percent of calories from fat, fiber and fruit and vegetable intake were also estimated using a food-frequency questionnaire.

"Many people think that a weight-loss program has to mean always feeling hungry," McTiernan said. "Our study suggests that snacking may actually help with weight loss if not done too close to another meal, particularly if the snacks are healthy foods that can help you feel full without adding too many calories."

Nationwide surveys indicate that 97 percent of U.S. adults report snacking, and such behavior is consistent across age groups. One study that surveyed a national random sample of more than 1,500 adults found that the most commonly preferred snacks were salty and crunchy items such as potato chips, pretzels and nuts; baked goods such as cookies and cakes; fruits; and ice cream.

Not all snacks are created equal, however. Foods less conducive to weight loss include empty-calorie items that contribute fat, salt, sugar and little nutritional value, such as potato chips and sugar-sweetened beverages.

For a woman on a weight-loss diet, a healthy snack should pack a nutritional wallop without breaking the calorie bank. "Since women on a weight-loss program only have a limited number of calories to spend each day, it is important for them to incorporate nutrient-dense foods that are no more than 200 calories per serving," McTiernan said. "The best snacks for a weight-loss program are proteins such as low-fat yogurt, string cheese, or a small handful of nuts; non-starchy vegetables; fresh fruits; whole-grain crackers; and non-calorie beverages such as water, coffee and tea."

The National Cancer Institute funded the research and participated in the study, which also involved investigators from the University of Washington and the University of Illinois at Chicago.

Study Information

Angela Kong, Shirley A.A. Beresford, Catherine M. Alfano, Karen E. Foster-Schubert, Marian L. Neuhouser, Donna B. Johnson, Catherine Duggan, Ching-Yun Wang, Liren Xiao, Carolyn E. Bain, Anne McTiernan
Associations between Snacking and Weight Loss and Nutrient Intake among Postmenopausal Overweight to Obese Women in a Dietary Weight-Loss Intervention
Journal of the American Dietetic Association
2011 December
Fred Hutchinson Cancer Research Center.

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