Is snacking between meals bad for your health? It depends on what and when the snack is

There was a time when the chorizo sandwich gave way to hummus and tomato with fresh cheese for the mid-shift snack at the SEAT plants in Barcelona. As part of a scientific study on nutrition, the automobile company replaced white bread and processed sausages in the snacks and offered its workers healthier alternatives. In all, about 600 of the 14,000 employees at the company participated in the project, which had the approval of the work council after tasting the new snacks. As a result of this study, there was an improvement in the life habits and health status of the participants. But apart from replacing the chorizo sandwich for a healthier option, something else shone through: snacking, depending on what and when it is, can be more or less beneficial for health.

Having a snack between meals is a very common habit — more than 90% of the public do so, according to a U.S. study — and snacks represent up to 25% of total daily energy intake in the U.K. and U.S. and between 14% and 31% in Europe. But the scientific community still limits its benefits or drawbacks to health. According to the experts and the literature we consulted, everything depends on what people snack on, how much, and when. “Whether eating a snack is considered beneficial or harmful behavior is largely based on how ‘snack’ is defined. The term tends to connote energy-dense and nutrient-poor foods, such as cakes, cookies, chips, and other savory snacks and sugary drinks (...) However, it can also refer simply to an occasion to eat between breakfast and lunch, or lunch and dinner,” two researchers from the University of Minnesota put forward in an article in 2018. The very definition of a snack, a light bite, or a tidbit makes it difficult to study its effects on health and “complicates its dietary reputation,” the American scientists point out. But not everything is black or white when it comes to snacking.

In fact, although the frequency of meals and its relationship with obesity and cardiovascular health have been widely studied, scientists are not clear about whether it is more beneficial to eat a few or many times a day. For example, there is no robust evidence that it is better to eat two, three, or four meals, nor do they know the long-term effects of the opposite: intermittent fasting. A review in 10 European countries revealed that the usual frequency with which people ate varied between five and seven times per day. “There is some support that increased eating frequency has a beneficial impact on markers of cardiovascular health, but the quality of this support remains weak,” the Minnesota researchers admit. And they suggest that these effects may fluctuate depending on the individual’s body mass index (BMI), food choices, or motivation for snacking. It all depends.

Ramon Estruch, a doctor at the Hospital Clínic de Barcelona and coordinator of the Predimed study, which is researching the impact of the Mediterranean diet on health, explains the origin of the recommendation to eat five times a day: “There was a tendency to recommend eating something at mid-morning and mid-afternoon so as not to be too hungry at mealtimes. Snacks would be good for that: to avoid compulsive eating.” The doctor, who was also the lead researcher in the study with the SEAT workers, admits, however, that the scientific community is now navigating “troubled waters,” among other things, due to the potential benefits that intermittent fasting can have on longevity.

Estruch summarizes the evidence on snacks: “They help provide energy when there are many hours between meals and also reduce the appetite for the next meal, so the amount we eat is reduced. They can also provide extra nutrients if they are healthy (fruit, nuts). The disadvantage is that snacks can provide an excess of calories and if they are ultra-processed, they add salt, simple sugars, and saturated fats, to the detriment of our health.” Recently, a group of researchers from King’s College London presented preliminary data from a study specifically about the benefits (or not) of snacking between meals at the American Society of Nutrition congress. Their findings were that “the poor quality [of snacks] and late-night snacks are risk factors for cardiometabolic health, but high-quality snacks may have health benefits.”

The quality of the snack is key

It all depends on what is eaten and when it is ingested, agrees Jordi Salas-Salvadó, Professor of Nutrition at the Rovira i Virgili University and head of research into obesity and nutrition with the CIBER public health consortium at the Carlos III Institute of Health: “The quality of the snack is very important. Snacking on healthy things does not have the same harmful effects on health.” And he gives an example: “At mid-morning, if you eat some bread with a little salt, it is followed by a very high glycemic peak and, four hours later, your blood sugar drops, you have a ferocious appetite, and you have to eat more. If you eat a handful of nuts instead, that peak does not occur, and you are not as hungry after a few hours.”

And for “bread with a little salt,” read “popcorn, nachos, pastries, chips...” Any type of carbohydrate, the specialist explains, which makes sugar rise sharply. “Continuous snacking that produces postprandial glucose peaks is harmful because it is related to obesity,” he says. When these carbohydrates make sugar rise quickly, Salas-Salvadó explains, “the pancreas secretes insulin, the cell captures glucose and uses it; but after three hours, the sugar drops a little more than normal, and the brain realizes that and causes you to be much hungrier, giving you a ferocious appetite.” However, healthier snacks, “such as guacamole and cucumber, hummus and carrots, or yogurt with strawberries,” the scientist says, do not produce these glycemic spikes.

Among the consequences of unhealthy snacking between meals is the risk of putting on weight, due to the extra energy contribution it entails. In this sense, a scientific review found, in fact, that the consumption of high-energy snacks can contribute to increased food intake and weight gain in adult populations, but the researchers also emphasized that “the context in which snacking takes place, such as eating them alone or outside the home, late in the day, or in front of the television, are also important for this behavior.” The scientists point out, on the other hand, that motivation is another key variable, since these snacks can be eaten for various reasons, such as hunger itself, food culture, distraction, or boredom, among others. “Some studies suggest that eating when we are not hungry, or without a biological signal, is associated with higher caloric intake,” the Minnesota researchers note.

Another study also highlighted the influence of these context factors, emphasizing that “pre-existing health status may influence snack choice and its effect on weight.” On this point, an investigation from the University of Cambridge with 10,000 adults described that snacking has a different relationship with health according to BMI: in people with a normal weight, the intake of snacks was associated with lower total body fat in men and women, while in those who were overweight or obese, snack intake was associated with a wider waist circumference and subcutaneous fat in women and with a wider waist circumference in men. The people with a higher BMI, in addition, “had a higher intake of chips, sweets, chocolates, and ice creams and a lower intake of yogurt and nuts compared to normal-weight participants,” the scientists found.

The danger of late-night snacks

The time we choose to snack is also key. Snacking at night, after dinner, is not a good idea. “Obesity is closely associated with eating at night and, in fact, there is a nocturnal psychological alteration: they are night eaters, who devour carbohydrates at night. There are studies that associate night snacking with obesity and this may be due to psychological issues or stress,” explains Salas-Salvadó. Estruch makes only one exception: “Diabetics are advised to have something to drink at midnight to avoid lowering their sugar levels too much.”

In an article published in Physiology & Behavior, scientist Richard Mattes of the Department of Nutrition at Purdue University (Indiana), concludes that while snacking is not “inherently problematic” and can even “be incorporated into healthy diets,” this must be done with “knowledge and vigilance.” “Although snacking can contribute important nutrients, this often comes with an energy cost that negatively outweighs the positive contribution to diet quality. Snacking is a relatively new behavior, but it is likely to persist. Learning to turn it into a positive intake behavior must be a priority,” he says.

Regarding the anecdote of the chorizo sandwich in the SEAT workers study, vending machines with healthy products also came to stay at the factory plants. The study was completed, but workers continue to have vending machines with apples, yogurt, or fiber cookies at their disposal.

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