A response to Harriet Hall on "Fed Up"

(Introductory note: this is a post that had been sitting in my blog's draft folder for almost 2 years, which I decided recently to finish and publish. Enjoy!)

In a 2014 blog post on Science-Based Medicine, Harriet Hall attempts to debunk the then-recently released movie "Fed Up", which pointed the finger at Big Sugar as a (possibly even the) main culprit in the obesity epidemic. She seems to disagree with this conclusion and thinks that other factors explain the obesity epidemic than does the increase in sugar consumption in recent years. In this post I will scrutinize her attempts to scrutinize the claims in Fed Up.

First, she tackles the issue of whether there is a correlation between sugar consumption rates and obesity rates. She states that: 

Correlation is not causation, even when there is a strong correlation like the one between the rise in autism diagnoses and the rise in the sales of organic food. There is no such strong correlation between sugar consumption and obesity, much less any convincing evidence of causation.

Sugar consumption has actually decreased around the world even as the rate of obesity has continued to climb. Between 1999 and 2008, American consumption of added sugars decreased from 100 g/d to 76 g/d, mainly due to a reduction in soda consumption."

She is citing a study from 2011 that did indeed reach that conclusion, albeit only with respect to America, rather than "around the world". However, another study, published the month after Hall's blog post (which I therefore won't blame her for not mentioning), found that between 1977 and 2009, added sugar consumption in America increased by over 30%. Globally, sugar consumption trends seem to differ markedly depending on who you ask: one review found that they were "either stable or decreasing in both absolute (g/d) and relative (% energy) terms," while other data suggests that global sugar consumption increased significantly from 2009 to 2015. Also, contrary to Hall's implication that obesity rates "have continued to climb", in America at least, obesity rates have been mostly flat from 1999 to 2010. As for worldwide, to be fair, it seems obesity rates are increasing over the long term (1980-2011). 

Given that the jury still seems to be out on this point, let's move on to Hall's subsequent arguments. For instance, she tries to analyze correlations between sugar consumption and obesity rates and comes up with null results:

This webpage lists per capita sugar consumption by country, and it clearly does not correlate with rates of obesity in those countries. Countries with higher per capita sugar consumption than the US include Argentina, Australia, Austria, Belarus, Belgium, Brazil, Chile, Denmark, Estonia, France, Georgia, Germany, Iceland, Malaysia, Malta, Mexico, Morocco, Netherlands, New Zealand, Norway, Poland, Slovakia, Sweden, Switzerland, Ukraine, UK, and Venezuela. According to this source there are 17 countries with higher rates of obesity than the US. Not a single one of those countries has a higher per capita sugar consumption than the US.

On this basis, she states that:

...it’s premature to make the kind of definitive pronouncements that the film makes about the role of sugar [in causing obesity]. 

Peer-reviewed studies (which, though this may seem hard to believe, I trust more than blog posts) suggest Hall is wrong, though. One, for example, found that "High sugar consumption and sedentary lifestyle are associated with increased obesity prevalence." Another found that "Soft drink consumption is significantly linked to overweight, obesity, and diabetes worldwide, including in low- and middle-income countries." Note: most research on this subject seems to focus on soft drinks rather than added sugar overall. According to the NHS, 25% of added sugar people consume comes from sugary drinks. A 2006 estimate from Harvard Researchers was higher (47%), and these researchers said in 2013 that sugary drinks are "the largest contributor to added sugar and top sources of calories in the US diet".  Thus, focusing specifically on sugary drinks seems like a reasonable approach.

Hall then criticizes Gary Taubes, who appears in the movie, for promoting low-carb diets. Rather than citing studies or looking at data, she cites the case of Chris Voigt, who ate only potatoes for 60 days and lost 21 pounds, the opposite of what Taubes would have us believe would happen. Voigt also lowered his cholesterol by 67 points after this diet ended. What Hall doesn't mention is that Voigt is the head of the Washington State Potato Commission, meaning it's literally his job to promote potatoes. Anyway, the validity of one anecdote is very limited, as Hall herself acknowledges, pointing out that Voigt's test was "informal". She then moves on to the main thesis of Fed Up: that sugar causes obesity. She argues that:

The sugar/obesity hypothesis has not been properly tested either. There are plenty of examples of people who eat a lot of sugar and processed foods and don’t gain weight. In fact, one obese boy in the film complains that his brother eats the same way he does but doesn’t gain weight. There are plenty of examples of people who have lost weight and kept it off by reducing calorie intake and increasing exercise. We know some of the factors involved in successful weight loss, and eliminating sugar is not on the list.

Ah, finally, some actual evidence (though only toward the end there), rather than more of the anecdotes with which Hall seems to be so smitten. The paper Hall is citing says that some successful weight loss strategies are "eating a diet low in fat, frequent self-monitoring of body weight and food intake, and high levels of regular physical activity." However, not only is this paper more than a decade old, other studies suggest that eliminating sugar consumption is associated with weight loss. A 2012 study found that "Masked replacement of sugar-containing beverages with noncaloric beverages reduced weight gain and fat accumulation in normal-weight children." For adults, another study found that "a reduction in liquid calorie intake of 100 kcal/d was associated with a weight loss of 0.25 kg."

Next, Hall states that:

Colin Campbell of the Center for Nutritional Studies points out that the evidence showing sugar to be a major factor in obesity is relatively weak and is confounded by total calorie intake and other factors. He says:

I know of no evidence that were we to eliminate all sugar from our diets, presumably leaving the rest of the diet the same, we could rid ourselves of disease and restore our health.

Sure, Campbell has said this, but he is contradicted in this regard by a systematic review and meta-analysis published in BMJ in 2013, which concluded that "Among free living people involving ad libitum diets, intake of free sugars or sugar sweetened beverages is a determinant of body weight."
This is in line with a more recent review, which found that "Sufficient evidence links a high intake of sugar to dental caries and obesity, and high intakes of sugar-sweetened beverages in particular to increased risk of type 2 diabetes."

Towards the end, Hall states, "I favor education over regulation. I’m not against regulating the food industry, but I would like to see proposals tested before they are widely implemented...We can’t just assume that any proposed remedy for the obesity epidemic will work. No matter how slam-dunk it sounds, it must be tested using scientific methods." In fact, however, the evidence that reducing consumption of sugar-sweetened beverages will be effective in reducing obesity and related conditions is compelling. When two Harvard researchers reviewed the literature on this subject in 2015, they found that the results of randomized controlled trials "...provide strong evidence that decreasing consumption of SSBs significantly reduces weight gain and obesity in this age group [i.e. adolescents]."
Conclusion: Hall doesn't really seem to do a good job of addressing the empirical evidence most relevant to the link between sugar and obesity, and the evidence that does exist on this subject indicates that sugar is a major contributor to rising obesity rates. This is not to say that Fed Up is totally accurate, but that its basic point is much more valid than Hall would have you believe.