Have starch from grains and fat, but not fructose, been significant contributors to obesity?


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Have starch from grains and fat, but not fructose, been significant contributors to obesity?

Related tags Nutrition Obesity

Increased energy intakes primarily from starch in grains and fat may have significantly contributed to sky rocketing obesity rates in the US, but not fructose, according to a new analysis of 40 years-worth of data from the USDA.

Obesity rates have risen from about 13% in 1970 to about 35% in 2009, with changes in the composition of food debated extensively by academia and industry. Dietary fructose has been blamed by many as a possible contributor to obesity rates, but a new analysis found that total fructose availability in the US did not increase over the four decades between 1970 and 2009.

Trevor Carden and Timothy Carr from the Department of Nutrition and Health Sciences at the University of Nebraska used the USDA Loss-Adjusted Food Availability Database in combination with the USDA Nutrient Database for Standard Reference to elucidate if fructose consumption has increased sufficiently in the US to contribute significantly to the prevalence of obesity.

Writing in the open-access Nutrition Journal​, they report that the availability of carbohydrates has increased more than any other macronutrient in the US food supply over the last 40 years. Compared to 1970, 32.3 grams more of carbohydrates were available per day in 2009.

Other studies have reported that fructose consumption increased 18% between 1970 and 2004, but the new analysis of Carden and Carr found fluctuations in fructose availability over 40 years, with an overall result of no net change in total fructose availability.

“Despite the current findings showing a lack of association between total fructose availability and obesity prevalence, one should not regard fructose as a benign nutrient that can be consumed without consequence, particularly if over-consumed,”​ wrote the researchers. “Fructose is a lipogenic nutrient and metabolized differently than glucose.

“The current study suggests that the unique lipogenic properties of fructose may have been of minor importance to the rise in obesity due to the small contribution of dietary fructose relative to glucose and total energy availability.”

“The present findings also cast doubt on the purported role of HFCS as a singly important dietary factor in promoting obesity. Despite increased usage of HFCS in the US food supply, no net change in total fructose availability occurred between 1970 and 2009 when analyzed using loss-adjusted data.”

Total calories drive obesity rates

The new analysis, which was supported financially by the University of Nebraska Agricultural Research Division with funds provided through the Hatch Act, was welcomed by the Corn Refiners Association (CRA).

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“The current study suggests that the unique lipogenic properties of fructose may have been of minor importance to the rise in obesity"

“This study confirms what the scientific evidence has shown for years. Consumption of fructose is not a unique factor in the rise in obesity rates in the US,” ​said CRA in a statement.

“As the researchers conclude, claims that fructose is somehow uniquely responsible for our nation’s obesity epidemic are not only wrong, they are counter-productive to finding effective solutions to this complex health crisis.

“As the data shows, it is the increase in total calories that is driving the increase in obesity rates. Virtually all of these additional calories are in the form of grains and fats, whereas fructose-containing sweeteners such as sugar and high fructose corn syrup account for only 1.3% of the increased calorie consumption since 1970.

“High fructose corn syrup consumption has decreased steadily for more than 10 years. In 2012, Americans consumed 25% less of it than they did in 1999 while obesity rates continued to climb during this time period.”

Study details

Carden and Carr analyzed food availability per capita for 132 individual food items, and results showed that total energy availability increased 10.7%, with zero net change in total fructose availability. Energy from carbohydrate, fat, and protein increased 9.8%, 14.6%, and 4.7%, respectively.

“The food categories that increased the most during this time were grains and fats/oils, having increased 24.2% and 25.3%, respectively,”​ said the researchers. “Caloric sweeteners (including both sucrose and HFCS) increased a modest 1.3%.

“When expressed in terms of monosaccharides available for metabolic absorption, all carbohydrate food sources provided [greater than] 3-times more glucose than fructose. Moreover, total glucose availability increased 13.0% from 1970 to 2009, whereas total fructose availability did not change.”

“Our findings indicate that fructose per se was not a unique causal factor in promoting obesity during 1970-2009. Rather, we conclude that increased total energy intake, due to increased availability of foods providing glucose (primarily as starch in grains) and fat, to be a significant contributor to increased obesity in the US.”

Source: Nutrition Journal
12:​130, doi:10.1186/1475-2891-12-130
“Food availability of glucose and fat, but not fructose, increased in the US between 1970 and 2009: analysis of the USDA food availability data system”
Authors: T.J. Carden, T.P. Carr

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