Unhealthy snacks undo the benefits of an otherwise healthy diet

Snacking is big business. In 2021, retail snack sales grew by 0.8 percentage points to reach $620 billion, according to Euromonitor International.

Snacking is also a hugely common habit for millions of people. Market analysts at Euromonitor predict that the prevalence of “snackification” will grow over the next five years, describing this phenomenon as “new consumption occasions for hybrid lifestyles”.

Data from a peer-reviewed, open-access study published last month in the European Journal of Nutrition seems to confirm this: 95% of the UK participants ate at least one snack a day and almost one-quarter (24%) of participants’ daily energy intake came from snacks such as cereal bars, pastries, and fruit. Forty-seven percent of people ate two snacks a day and 29% had more than two.

However, contrary to public opinion, snacking is not necessarily unhealthy – as long as the snacks are nutritious, the researchers concluded.

The impact of unhealthy snacking

For the study, scientists from the King’s College London and ZOE, a personalised nutrition startup co-founded by Professor Tim Spector, used data on factors such as demography, diet, stool metagenomics, cardiometabolic blood markers, and anthropometrics markers, and combined them with self-reported information on snacking habits, including frequency, quality, and timing.

They found that unhealthy snacks and sugary drinks between meals may be fuelling metabolic health problems, even among people who eat otherwise healthy and balanced meals.

More than one-quarter (26%) of participants reported eating healthy main meals but poor-quality snacks such as highly processed foods and sugary treats. The result was that they reported feeling hungry and had poorer health markers such as a higher BMI, higher visceral fat mass, higher postprandial triglycerides concentrations, higher fasting insulin, and insulin resistance. All of these markers are associated with metabolic disease such as stroke, cardiovascular disease, and obesity.

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Defining healthy and unhealthy snacks

Conversely, people who often snacked on high-quality foods were more likely to have a healthy weight compared with those who didn’t snack at all or those who snacked on unhealthy foods. Good-quality snacks may also lead to better metabolic health and decreased hunger, the study showed.

High-quality snacks, including whole fresh fruit and vegetables, nuts, and seeds, tend to be high in fibre and other healthy nutrients and have retained their food matrix structure; in other words, they are not ultra-processed.

However, such healthy, whole-food snacks make up an ever-shrinking proportion of the UK’s snack basket. Ultra-processed foods are believed to account for 50% of British people’s energy intake, and the most consumed snacks are energy-dense foods such as confectionery, packaged savoury snacks, and sugar-sweetened beverages.

Timing matters

The researchers also found that timing matters. Individuals who snacked after 9pm had higher postprandial glucose and higher postprandial triglycerides compared with people who snacked at other times during the day. What’s more, night-time snacking is common: almost one-third (32%) of all participants were classified as late-evening snackers.

“Our research supports increasing intakes of high-quality, minimally processed snacks, given their positive impact on health,” the scientists wrote, concluding that snack quality and the timing of consumption were “simple diet features” that may improve diet quality with potential health benefits.

ZOE’s chief scientist Dr Sarah Berry, from King’s College London, said: “Considering 95% of us snack, and that nearly a quarter of our calories come from snacks, swapping unhealthy snacks such as cookies, crisps, and cakes to healthy snacks like fruit and nuts is a really simple way to improve your health.”

Her King’s College London colleague Dr Kate Bermingham, senior scientist at ZOE, said the study contributed to the existing literature that food quality is the driving factor in positive health outcomes from food.

“Making sure we eat a balanced diet of fruit, vegetables, protein, and legumes is the best way to improve your health,” Bermingham added.