The latest recommendations from the Dietary Guidelines Advisory Committee have unleashed a maelstrom of vitriol from processed food companies. The group of 14 independent scientists  eased its restrictions on fat and cholesterol while declaring sugar a major dietary villain. The guidelines would limit the amount of sugar that food companies could covertly add to their products, based on the growing body of science that links consumption of excessive sugar to type 2 diabetes, heart disease and fatty liver disease.

The food industry has fired back, saying that such limitations are not based on sufficient science. It insists that “a calorie is a calorie,” that the source is inconsequential to the consumer’s health. If you’re fat, it’s your fault, the industry says — limits on sugar won’t prevent people from overeating.

Even Congress is choosing sides. Rep. Robert Aderholt (R-Ala.) introduced a House bill to limit federal nutritional guidelines only to those based on “robust” scientific evidence (e.g. randomized controlled trials, like those that evaluate medicines). These DGAC recommendations to the USDA are based on “moderate” evidence (prospective correlation studies or natural history studies, like those linking smoking with tobacco use).

The problem is that clinical nutritional data almost never reach robust proof, because you can’t change the diets of people for 50 years to see if they develop more diabetes or heart disease; it’s expensive, unethical and unlawful. Scientists have shown that adding extra sugar to people’s diets worsens cardiometabolic risk factors, such as high triglycerides, blood pressure, glucose and insulin levels, or low HDL — all components of what is called “metabolic syndrome.” But these studies can present various possible causes for the negative medical outcomes — extra calories, excess weight or extremely high levels of sugar well beyond a typical diet. Metabolic syndrome affects about 35 percent of American adults, but proving that excessive intake of added sugar directly causes these diseases in humans has been tough.

A study published this week should help. I worked with a group of researchers and found that, after just nine days of eliminating added sugar from the diets of extremely obese children, their symptoms of metabolic syndrome significantly diminished. Our study, published in the journal Obesity, establishes a direct relationship between added sugar and these chronic diseases, unrelated to its calories or its effects on weight. During the study, we catered all meals for 43 obese children for nine days, substituting starch for sugar in all processed foods. We took the chicken teriyaki out and put the turkey hot dogs in. We took the sweetened yogurt out and put the baked potato chips in. We took the pastries out and put the bagels in. They could eat processed “kid food” as long as there was no added sugar. Their fat and protein content was kept the same, and we gave them enough extra calories to maintain their weight.

In short, every aspect of their metabolic health improved: Their average diastolic blood pressure decreased by 5 mmHg, and their triglycerides (high levels of which are a risk factor for stroke) decreased by 33 percent. Their LDL cholesterol level and fasting blood glucose also fell, and their liver function tests improved — all without changing the children’s calorie intake or weight and without exercise. We simply substituted starch for sugar in their processed food and watched their health improve.

This is not correlation. It’s causation — the most robust evidence of all.

Some have criticized the study because it didn’t include an external control group to which we could compare the children’s health outcomes. But it would have been impossible to have an adequate external control group, given that people consistently underestimate how much they eat, especially sugar. If we provided a control group with meals according to their self-reported diets, we would have been underfeeding them. Instead, we implemented multiple internal controls, including feeding the children as much as necessary to maintain their weights. In fact, some children felt engorged with food because of how much they had to eat to keep their weights up on a diet with no added sugar. Some of the children lost weight anyway, but in those cases, the lost weight came from water and/or muscle — neither of which would contribute to their improved metabolic health.

Others critics have said our sample size is too small for the results to be significant. But it’s important to recognize that the results were consistent in every child — everyone’s metabolic health improved a lot. There was not a single outlier.

Our research demonstrates that a calorie is not a calorie. Where those calories come from determines how they’ll affect your body. And sugar calories are the worst, because they turn to fat in the liver, driving insulin resistance and increasing the risk of diabetes, heart and liver disease. Metabolic syndrome can affect thin people, too, which explains the high rate of diabetes in India and China despite the relatively low prevalence of obesity.

To turn our epidemic of metabolic syndrome around, the food industry must reduce the sugar it surreptitiously adds to processed foods. Even Mars, the candy company, has broken ranks with the food industry and supported the DGAC recommendations. In May, the company said it supports displaying added sugar levels on nutritional content labels and agrees with recommendations to limit sugars — particularly added sugar — to no more than 10 percent of daily caloric intake; right now Americans average 16 percent. The world’s largest candy company gets it! (Mars, it’s worth noting, is a private company, not beholden to shareholders and Wall Street.)

Science should drive policy, but the politics get in the way. And politics is based on money. The food industry nets about $450 billion per year, yet America wastes at least $830 billion per year caring for diseases linked to metabolic syndrome, including diabetes, heart disease and dementia. This is unsustainable, and a major reason why Medicare and Social Security will be broke by 2030. The USDA must do the right thing and curb Americans’ consumption of added sugar, rather than kowtowing to the processed-food industry.

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