What Science Says about Snacking

American dining may have evolved from Old World custom into the "three square meals" tradition of the 20th century, but today's consumers are snackers. In fact, over the last four decades, more Americans have traded in meals for snacks.

Between-meal noshing supplies nearly one-quarter of daily calories, earning snacks the status of "fourth meal." What's more, since the late 1970s, daily calorie intake has increased among men and women, with the majority of additional calories consumed between meals. A 2011 report from the U.S. Department of Agriculture claims Americans snack twice as often as they did in the late 1970s, although newer analysis of the data suggests the frequency of snacks has stayed the same while total calories have increased.

These figures have led some experts to ask how snacking affects body weight and other health concerns.

How and Why We Snack

While some people eat between meals because they hold a vague notion that frequent eating is healthful, others report snacking to satisfy cravings for sweet or salty foods, prevent or relieve hunger, boost nutrient intakes, control weight, rev their metabolic rates, pass the time, deal with unsettling emotions or replace meals.

According to a 2014 Nielsen report, 41 percent of North American respondents ate snacks instead of dinner at least once in the previous 30 days. The favorite snacks in North America are chips, chocolate and cheese, according to the report.

Fresh fruit landed fifth in popularity, with 55 percent of survey respondents reporting they ate fresh fruit for a snack at least once in the previous 30 days. A separate study reported that adolescents who snacked most often were the most likely to skip meals. All-day grazing and frequent snacking instead of structured meals and snacks may be side effects of today's on-the-go lifestyle.

Does Snacking Affect Weight?

Snacking may help control appetite, or it may contribute to recreational eating and excess calories. Research supports both opposing views. Beginning in the 1960s, studies noted that people who ate the fewest number of times during the day had the greatest amount of excess body weight, leading many health professionals to recommend frequent eating as a weight-loss tool.

More recently, researchers have challenged the idea that eating frequently aids weight control. A widely recognized problem in diet studies is underreporting of food and calorie intake by some participants. When researchers removed data of people they suspected gave faulty information, the results suggested that the more often someone ate, the higher his or her body mass index would be. Spanish researchers found that people who identified themselves as usual snackers were most likely to gain significant weight during the study's 4½-year follow-up period. Plus, they were nearly 70 percent more likely to become obese.

Among teen girls, eating frequently at the beginning of the study predicted less body fat a decade later. And a study of nearly 2,700 men and women in their 40s and 50s found those who consumed solid food six or more times in 24 hours took in fewer calories and had a lower mean BMI compared to participants who ate solid foods fewer than four times daily.

Conflicting data may be the result of many factors, such as the way researchers defined a snack or eating occasion, whether or not caloric beverages were included in the analyses and underreporting of food, beverage and calorie intake, which can make dietary assessment tools invalid. Reverse causality also may be at play, meaning that some people with higher BMIs may choose to eat less frequently in attempt to lose eight — not that they are heavier because they eat less often.

Though population studies show inconsistent results, randomized intervention trials allowing subjects to choose what they eat generally show no effect on body weight. Of five short-term studies comparing high and low eating frequencies, only one showed a slight advantage when subjects consumed more meals and snacks. Sixteen adults with high cholesterol levels consumed the foods they typically ate, but either as three or nine meals daily for four weeks. Participants eating more often lost an average of 0.9 pounds, while those on the less-frequent meal pattern dropped only 0.2 pounds. In a two-month weight-loss program combining meal replacements and regular food, weight loss was the same whether participants consumed three daily meals or three meals plus a bedtime snack.

Although some dieters snack to boost their metabolic rates, research suggests these efforts are in vain. Studies that examine data for up to 48 hours after eating find that the jump in metabolic rate or the thermic effect of food is not dependent on meal frequency. Rather, overall metabolic rate is similar when a specific amount of food is eaten during few or many occasions. Since frequent eating doesn't appear to burn more calories, researchers looked at the opposite side of the energy balance equation: Does frequent eating cause people to consume fewer calories? One review found a slight benefit to appetite control when eating six meals per day compared to three, and that eating fewer than three meals per day is unfavorable for appetite control.

Both the Evidence Analysis Library of the Academy of Nutrition and Dietetics and experts at a 2009 symposium on eating frequency and energy balance concluded that scientific evidence pointing to an ideal eating frequency for weight control doesn't exist at this time.

Snacking on Other Metabolic Effects

Eating frequency has the potential to affect metabolic parameters other than weight and body fat. In the two-month meal replacement study previously mentioned, there were no differences in cholesterol or triglyceride levels between those eating either three or four times daily.

However, when seven healthy men consumed identical diets as either three daily meals or 17 daily "nibbles" (defined as smaller than a regular snack) for two weeks, cholesterol measurements were better with the nibbling pattern. This study has limitations due to its small sample size, so more research is needed to support the findings.

Additionally, two single-day studies found improvements in blood sugar and lipids when adults with Type 2 diabetes ate more often. But a four-week study among people with Type 2 diabetes found no such advantage when comparing nine small meals to three larger meals and one snack.

Even if long-term benefits were likely, would many people want to eat up to 17 times per day?

Snacking and Diet Quality

Snacks may boost diet quality or lead to excess intakes of solid fats, added sugars and sodium. Although experts debate the health value of snacking, nearly all agree that the type of snack matters. A study of 233 adults in a worksite wellness program found that total snacking calories and frequency of snacking were unrelated to diet quality or BMI. However, the choice of snack foods affected both. The percentage of snacking calories from nuts, fruit and 100-percent fruit juice was related to better diet quality, while percentage of snacking calories from sweets and sugar-sweetened beverages was related to poor diet quality. Eating vegetables as snacks was associated with lower BMI, and eating sweets was associated with higher BMI.

While there is considerable interest in eating frequency, there is no consensus regarding an ideal pattern. It may be that meal and snack quality is more important than frequency of eating and that consumers can benefit from any number of meal patterns. As research into these factors continues, the best pattern may be the one most suitable to a person's individual lifestyle.

Jill Weisenberger on EmailJill Weisenberger on FacebookJill Weisenberger on GoogleJill Weisenberger on LinkedinJill Weisenberger on PinterestJill Weisenberger on TwitterJill Weisenberger on Youtube
Jill Weisenberger

Jill Weisenberger, MS, RDN, CDE, CHWC, FAND, is a writer, nutrition consultant and speaker with a private practice in Newport News, VA, and is the author of four books, including the bestselling Diabetes Weight Loss – Week by Week and her newest title, Prediabetes: A Complete Guide. Follow her on social media and learn more at jillweisenberger.com.