Is Sugar Making You Fat? (MYTH BUSTED with Science)

Welcome to another part of the Myth Bust series, where we examine a common fitness or nutrition myth, look at where the myth comes from, and why it’s wrong based on an objective look at the scientific literature. 

Today, we’re going look at the idea that sugar makes you fat.

Where Did This Myth Come From?

In 1972, Professor John Yudkin published a book titled Pure, White, and Deadly: How Sugar is Killing Us, and What We Can Do to Stop It.

In my opinion, this book was one of the first to open the public up to the idea that sugar is an enemy to our health. However, the book didn’t gain quite as much acclaim initially as it has now.

That’s because just two years earlier, Ancel Keys published the iconic “Seven Countries Study” (1) shifting the public’s attention away from sugar and onto dietary fat. That shift lasted for decades.

However, sugar has been in the spotlight recently. In 2003, a review article published in the American Journal of Clinical Nutrition suggested that “there are important similarities between the trend in HFCS (high-fructose corn syrup) availability and the trends in the prevalence of obesity in the United States.” (2)

The authors also correctly noted that fructose and glucose have different metabolic effects, especially in regard to insulin release and metabolism in the liver.

Therefore, they singled out fructose as the main evil, rather than painting all sugars with the same brush. In addition, other systematic reviews (that didn’t adjust for total energy intake) also found a strong correlation between sugar intake and obesity.

So, after being exposed to Yudkin’s book, a pile of review articles, some systematic reviews, and many documentaries, I think it’s pretty reasonable that a large majority of the public has come to accept this idea as scientific truth.


Where Did It Go Wrong?

The main issue about the conclusions being drawn about sugar is that they make an unjustified jump from correlation to causation.

Just because two things are correlated, like sugar and obesity, it doesn’t mean that one is the cause of the other. To illustrate this point, it’s obvious that the correlation between cheese consumption and tangled bedsheet deaths does not imply that cheese causes death by bedsheets.

And while it is true that sugar-sweetened beverage consumption has risen just like obesity rates have risen, this correlation is the weakest form of evidence available, especially since other beverage consumption patterns, including bottled water (depicted in the graph below) have also demonstrated a strong correlation with obesity in the United States.

 A 2005 paper titled “Sugar and Health Controversies: What Does the Science Say?” concluded that, “sugar doesn’t make a unique contribution to obesity.” (3)

It also suggests that, “in a condition as complicated as obesity, it is highly unlikely that one single nutrient would uniquely cause this condition. It is more likely that the totality of the diet, including increased caloric consumption from all sources, exerts a significant impact on the likelihood of obesity.”

 For some more global insight on this, let’s take a look at Australia, where between the years of 1980 and 2003, despite a 23% drop in refined sucrose consumption, Australia still experienced a 3-fold increase in obesity. (4)

While epidemiological research like this is a weak form of evidence, the Australian Diabetes Council acknowledges that, “these findings support the supposition that once total energy intake has been accounted for, per capita changes in energy from sweeteners do not explain changes in the incidence of obesity.”

So, while the correlation is there, consumers of sugary drinks also tend to eat more calories over all. They tend to exercise less and smoke more, and have a poor diet in general. All these things can be difficult to measure and adjust for in epidemiological, observational research.

There is also some direct evidence suggesting that sugar clearly isn’t to blame for weight gain. 

For example, a massive 2013 systematic review looking at 68 studies found that if dietary sugar is replaced with other macronutrients, with a control for caloric content, there is no change in body weight. (5)

 The authors note that this finding strongly suggests that,“energy imbalance is a major determinant of the potential for dietary sugars to influence measures of body fat.” 

So, the question remains: if the evidence is so weak, why are so many members of the general public convinced that it’s true?

As highlighted in a 2013 review on the subject (6), the explanation comes down to 3 main factors:

1.     Emotion-Raising Language. 

Anti-sugar advocates often use words like “plague”, “evil”, “deadly”, and “dangerous” when describing sugar. We should be wary of this language, because it is a tactic used to heighten the impact of their claims.

2. The Distortion of Scientific Information

This occurs when weak, epidemiological or observational research is given more weight than it deserves, and a cause and effect relationship is falsely implied.

3. The Mere Exposure Effect

The more frequently you hear something, whether true or false, the more likely you are to believe it. Dictators and marketers have used this tactic for a long time. They know that repetition is key to getting the public to accept an idea.

While sugar probably isn’t the villain that it’s made out to be, it doesn’t mean that we can eat as much sugar as we want with no consequences.

The World Heath Organization recommends that added sugars make up no more than 10% of total calories. (7)

 However, they do admit that they base this recommendation largely on the well-established relationship between added sugars and dental cavities, since the “evidence related to sugars and weight change in adults was moderate to low.”

In a 2010 blog article “The Bitter Truth About Fructose Alarmism”, Alan Aragon suggests 50 grams as a safe limit for fructose intake for adults. (8

 If you estimate fructose as roughly 50% of your total sugar intake, that would leave you with about 100 grams for your sugar intake as a safe upper limit. Of course, this varies according to your specific lifestyle and your total caloric intake.

As a practical takeaway, here’s another important marketing tactic to be aware of:

While the research on the satiating effect of sugar is actually more mixed than many people believe, one 2017 paper on sugar and satiety suggests that people do tend to over consume at meals when sugary foods and drinks are labeled as “healthy”. (9)

In my opinion, sugar doesn’t appear to play a central role in either obesity or Type II Diabetes.

It’s more important to look at a person’s diet and lifestyle as a whole. Rather than villainize a single macronutrient, we need to be wary of foods that are high in salt and fat, highly processed, highly palatable, and very energy dense. We need to be aware of the food environment that we create in general.

Further Recommended Reading:

Jeff NippardComment