According to the ever-changing dietary guidelines of the campaign against obesity, fat is back in, but sugar is now out. Does the science behind this shift have any merit?
The cover of last week’s TIME Magazine features a curled shaving of butter, artfully back-lit, under the title ‘Eat Butter. Scientists labeled fat the enemy. Why they were wrong.’
The accompanying story describes how decades of research, health policy, and dietary trends were based on the faulty finding that fats, and in particular saturated fats, are bad for us. Of course, no sooner is one ingredient’s innocence established than a new nutritional foe is identified: sugar is now emerging as Public Enemy No. 1 among foodstuffs. The claim that sugar is the root cause of the obesity epidemic has become so mainstream that it even has its own documentary.
So is sugar just the next fat – will TIME be running an ‘Eat Sugar’ cover 20 years from now? Or is the science on sugar’s health effects more robust than the research on fat? Although the study of sugar is still in its infancy, the data so far offer convincing evidence that sugar consumption is linked to rising rates of obesity, diabetes, and associated diseases.
The leading proponent of this view is Robert Lustig, a researcher at the University of California, San Francisco. Lustig has been making the case against sugar for years – his website includes a collection of op-eds and interviews on the subject going all the way back to 2006. He argues that the amount of sugar added to processed foods, coupled with the lack of fibre in the Western diet, disrupts the balance of hormones like insulin and leptin that regulate eating behaviour and metabolic processes, leading to overeating, weight gain, and type 2 diabetes.
A key implication of this hypothesis is that cutting calories generally, without regard for the type of calories people are consuming, is not an effective strategy for combating the obesity epidemic. Indeed, one study found that young adults burned more calories on a low carbohydrate diet than on a low fat diet even though the diets contained an equivalent number of calories, indicating that what we eat affects how our bodies process food. As the study’s senior author, David Ludwig, explains, this can lead to a vicious cycle – eating sugar and refined carbohydrates disrupts our insulin system, causing us to overeat, and this leads to weight gain, which in turn engenders more overeating.
Not everyone supports this interpretation. A researcher at Columbia contends that refined carbohydrates cause weight gain because they are metabolized quickly and so tend to be consumed in large amounts. But even the skeptics agree that these carbohydrates affect the insulin system and that eating lots of sugar can affect risk for diseases like diabetes. Lustig and colleagues provided further evidence of this relationship in a recent analysis that compared data from 175 countries and found that higher sugar consumption is linked with higher prevalence of diabetes. This correlation was independent of obesity, indicating that, weight gain aside, a high-sugar diet can damage our health.
If the added sugar and refined carbohydrates in our food do cause overeating by changing how our metabolisms function, then it is going to take more than individual willpower to reverse rising rates of obesity and the diseases that accompany it. This is a point that Lustig and Ludwig take care to emphasize. In their editorials, they stress that we must stop blaming the obesity epidemic on people’s lack of resolve to diet and start acknowledging the role that society plays in shaping what we eat.
And they are right. There are all sorts of cultural forces that promote sugar consumption in our society, from the ubiquitous vending machines full of candy bars, to the jumbo-sized soft drinks available with every meal deal, to the cakes and sweets we bring to work to share with our colleagues. These products are crafted to induce habitual eating not just by packaging and marketing techniques but also by laboratory studies that fine-tune the ratio of salt, fat, and sugar to maximize focus group ratings and sales. Couple this with the effects sugar has on our metabolisms, and the barriers an individual has to overcome to change his eating behaviour are formidable. Simply put, changing diet requires changing deeply entrenched habits – habits that are cultivated by our culture and cemented by our physiology.
What can we do to change our high-sugar culture? Cracking down on the processed food industry – setting limits on the amount of sugar that can be added to products, regulating advertising, curbing portion size – is one obvious approach. Another, more positive strategy that holds great promise is embodied by the Edible Schoolyard Project. At schools involved in this scheme, students tend a school garden, harvest its produce, use this produce to prepare meals, and then share these meals together. The teachers even incorporate these activities into the curriculum – they teach early civilizations while planting grains and fractions while baking. Such programmes cultivate healthy eating by getting kids – and their parents and teachers – invested in their food at every step of its production, from the garden to the table. Regardless of which foodstuff is to blame for the obesity epidemic, creating a culture that promotes fresh food rather than processed products will make for a healthier society.