Abstract: The present obesity “epidemic” has been attributed to a growing trend for snacking. Snacking may contribute to excess energy intake and weight gain through different ways, for example: context/environment of eating, frequency of consumption and quality of food choices. The present article reviews data and hypotheses about the role of snacks in diet quality and body weight control. One obvious difficulty in this field is the diversity of definitions and approaches used in cross-sectional, longitudinal, and intervention studies. A brief paragraph reviews the prevalence of snacking in various countries and its recent evolution. The literature addressing the contribution of snacks to daily energy and nutrient intake presents two contrasting pictures. In many reports, snacking appears to facilitate the adjustment of energy intake to needs, and to contribute carbohydrates, rather than fats, to the diet, in addition to valuable micronutrients. Such results are usually reported in healthy, normal-weight children and adults. By contrast, snacking often appears to contribute much energy but little nutrition in the diet of other consumers, particularly obese children and adults. In addition to selecting energy-dense foods, eating in the absence of hunger in response to external non-physiological cues, in an irregular fashion, in contexts (e.g. while watching television) that do not favor attention to the act of eating, might be crucial factors determining the nutritional effects of snacking. While efforts should be continued to harmonize definitions and minimize the influence of under-reporting, interventions aimed at decreasing detrimental snacking should address both food-related aspects and behavioral components.
Alex’s Notes: Eating is a patterned activity, plain and simple. A perfect example is the cultural influence of society. The Western world, for instance, usually organizes eating into three daily meals: breakfast, lunch, and dinner. Unfortunately, as of late there has been an erosion of this traditional eating pattern, and the significance of this change is underappreciated. Food intake – both timing and frequency – has an intimate relationship with our biological clocks. Along these lines, it has been suggested that consuming “snacks” are a major driving force in obesity and its downstream health consequences. For clarity, the author refers to this as a trend for “grazing” rather than consumption of three traditional meals. Nonetheless, the contribution of snacking to the daily diet is one more subject for controversy in the scientific literature, and it begs exploration to see if snacking really is detrimental.
A “snack” is hard to define, however. In the U.S., “snack foods” are connotatively associated with “junk food” that are nutrient-poor and calorie-dense. No such definition exists in some other languages (like French), and this would fail to include many other foods that are regularly consumed in a “grazer’s” diet. A more conservative and agreeable definition of a snack would be any caloric intake outside the culturally accepted “main meals.”
Using the above definition, it is easy to see how prevalent snacking is in Western societies. Not a day can pass whereby we would not notice someone (adult or child) eating outside of the main meals. And you will observe this at every time of day (or night). For instance, a survey of over 16,000 university students across 21 European countries reported an average intake of 2.8 daily meals and 1.6 daily snacks. Moreover, it has been shown in America that both the daily number of eating sessions and the energy contribution from snacks has increased, while the time between eating occasions has decreased over the last 30 years among all ages. American children are moving toward three snacks per day, accounting for more than 27% of daily energy.
Can snacking be beneficial, or at least not harmful?
There are countless factors that are involved with this question, not the least of which is once again the culture in question. In a study of healthy lean French adults, meals were about twice as large as snacks in terms of energy and weight, and in these healthy, non-obese subjects, total energy and nutrient intakes were not different between days with and days without snacks, suggesting some form of daily energy compensation. Additionally, active normal-weight French children have been reported to consume more carbohydrate or protein-dense foods as snacks than their less active peers. It is not unreasonable to suggest that snacking is compatible with or even helpful to obtain adequate energy for daily needs, as well as important nutrients. However, this is entirely dependent on the food that is the snack.
On the flip-side, obese persons tend to select cakes, cookies, candies, chocolate, and other desserts more often than lean persons. They also tend to snack more. In U.S. children, the most common snack foods included high fat desserts and high fat salty snacks. And this is what is making up 27% of their daily energy intake. Clearly, besides the form of snacking behavior reported in healthy, lean individuals with a likely beneficial role in energy regulation and nutrient intake, there exists another form of snacking behavior characterized by the intake of high-fat and/or high sugar foods that can be associated with weight gain and obesity. This type of snacking constitutes an unquestionable risk factor since the high energy intake from snacks is not compensated for during regular meals.
The bottom line is that snacking is a grey area. It can easily facilitate energy and nutrient intake and ultimately its effects on the individual will be dependent on the composition of the snack and the ability of the individual to compensate later on. However, what is unquestionably unhealthy is eating nutrient poor, high energy foods at any time of the day (or night) in response to external stimuli of little relevance to nutrition (i.e. TV), in the absence of hunger, and/or in a context where no or little attention is given to the act of eating (again, TV).