The Romans built an empire on just one meal a day. The industrial revolution powered the trend for three solid repasts.
It wasn’t really until the 80s that grazing gained a cult following. Eating little and often prevents dramatic swings in blood sugar, increases calorie burning and decreases calorie consumption. Or so the theory goes. And it is a lucrative one. The global snack-food market – encompassing everything from more-ish Mars Bars to seemingly saintly seaweed strips – grew from $215.65 billion in 2021 to $236.11 billion in 2022.
The catch? Many scientific studies don’t actually support it. As one, published in 2015, put it: “increasing meal frequency does not appear to favourably change body composition in sedentary populations”.
Another study published that year concluded that: “In contrast to the conventional wisdom that modern humans eat three meals a day within a 12-hour interval… a large segment of the human adult population displays an erratic daily rhythm of eating”. Changing this, they wrote, could result in: “desirable health benefits”.
Could grazing, even on supposedly healthy snacks, be hurting, not helping, our health?
Blood sugar spikes
Dr Emily Leeming is Senior Nutrition Scientist at ZOE, the health app, based at King’s College London, where researchers are currently working on a paper devoted to snacking. Dr Lemming says even seemingly healthy choices can create unhealthy blood-sugar spikes when eaten as a stand-alone snack.
Consume some dried fruit as part of a balanced breakfast, and the fibre, fat and protein in its other ingredients would slow the passage of sugar into your bloodstream. Munch it from the pack, on the other hand, and you get an energy boost, followed by a crash that leaves you more likely to reach for a snack again, consuming more calories and elevating your blood sugar levels.
If you feel hungry, Leeming stresses, you should act. Have a balanced snack, or you put yourself at risk of making unhealthy food choices later, when you eventually cave in. “The problem is that if you’re not really hungry, and you’re just mindlessly grazing on snacks that aren’t balanced out with much protein, healthy fats or fibre, your blood-sugar levels can excessively rise and fall, your insulin will rise in response, and you risk a cascade of events that isn’t great for your health, over time.”
The odd day of snacking is not dangerous, she says. “But repeatedly, over the years, consistently excessive blood-sugar levels can start to do damage to your blood vessels, raising the risk of things like type two diabetes.”
Weight gain is another risk. Insulin, the hormone which regulates the amount of glucose in the blood, tells your cells to absorb what you’re eating. Its counterpart, glucagon, does the opposite: signalling to your body that it’s time to start burning energy from your stores. But glucagon is only released when insulin levels drop down to baseline – another argument for spacing out meals.
“One thing we do know is that tweaking your snacking habit is one of the quickest, easiest ways to make a change to your diet quality.”
Messing with metabolism
A 2019 study on rats showed that snacking causes weight gain and insulin resistance, whether that snack was healthy or otherwise. “There are almost no studies in humans comparing different meal-timing schedules to determine if one meal-timing strategy is better than the others,” notes Emily Manoogian, clinical researcher at the Salk Institute for Biological Studies, in her 2019 paper “When To Eat”. But your circadian rhythm – or body clock – uses your eating times to help set itself. “So eating at consistent times is important,” says Manoogian, “while irregular eating patterns have been associated with obesity, Type 2 diabetes, and cardiovascular disease.”
Skipping breakfast, for example, has been associated with late-night, high-fat and sugar snacking. But in the case three square meals vs a pattern of grazing on healthy, balanced micro-meals, the scientific evidence points to “different strokes for different folks”, says Professor Giles Yeo, author of Why Calories Don’t Count, who studies study brain control of body-weight at Cambridge University.
With one notable exception. Snacking after supper is especially likely to show up on the scales: “when you sleep, your metabolism drops,” he explains. “The calories you eat in the daytime are being taken on board at your time of maximum metabolic rate, while the calories you eat just before bed are going to go more into storage than into being burnt.” So stop shuffling to the fridge in your slippers.
And while the science is still in its infancy, there may be other downsides to those mid-morning morsels. “Eating, and in particular refined carbohydrates, causes inflammation," explains Professor Janet Lord, of the Institute for Inflammation and Ageing at the University of Birmingham. “Triggered at intervals, this process protects you from infection and isn't damaging. Sustained inflammation is what’s problematic – contributing to blood vessel damage, heightening your risk of heart disease, to bone and muscle loss too and even to dementia risk.”
Snack constantly and this is a potential risk: “Especially if you are older since, when we age, we end up with low level inflammation all the time, so layering more inflammation on top of that is problematic.”
What if you only snaffle those smug little bars and balls that are plant-based, or protein-powered? In the 1990s, a sweet snack meant a Mars Bar. In the noughties, it morphed into a cereal bar. According to a Euromonitor survey released this summer, the latest global trend is for healthy snacks, a market expected to grow to $152.5 billion by 2030. The labels on all these suggest a glut of guilt-free options… right?
“A calorie of protein makes you feel fuller than a calorie of fat, which makes you feel fuller than a calorie of carb,” says Yeo. “So a protein bar, as long as it’s not jammed-packed full of sugar, will make you feel fuller for longer. That’s an advantage to eating the protein bar over a Mars Bar.”
Yet Yeo says these often have the same amount of sugar as a chocolate bar. “No one eats a Mars Bar thinking they’re having a health food. But they don’t call these bars “high-protein high-sugar”: they only ever boast ‘high-protein’ on the packaging.” In fact, a study from Arizona State University, published last month [OCTOBER], found that people who ate a protein bar every day were more likely to gain weight than lose it, because many are so calorie-dense.
How about those raw bars, made of 100 per cent fruit and nuts? “If they’ve been pounded down to a goo, the fibre and protein are still in there, but your body has to do a lot more work to break it up, so it sits somewhere between a food without them and one with them.”
All of which means it might be time to empty that secret snack drawer. Or, if you feel the need, remember the old adage: an apple a day keeps the doctor away. Add a handful of seeds or nuts too. Just try not to eat them processed into a bar and squeezed onto a supermarket shelf.