Average sugar consumption in the United States has increased 50 percent since the 1970s, due in part to the use of high fructose corn syrup in beverages and other processed foods. The mechanisms by which added sugars lead to metabolic diseases such as obesity, type 2 diabetes, cardiovascular disease, and fatty liver disease have been explored in research using mouse models; however, the dose of sugar used in these animal studies is usually much larger than what is normally consumed by people. Authors of this report investigated the effects of human-relevant doses of added sugars on health and behavior in mice.

Mouse models are a useful tool in research because mice can be kept in environments where their exposure to light, food, socialization, and other environmental inputs is completely controlled, minimizing variation between mice when exposed to a dietary intervention. However, these highly controlled environments, combined with large doses of experimental foods, often limit the generalizability of mouse research for human health. Organismal performance assays, which use seminatural conditions to put experimental animals in direct competition with each other, more accurately measure survival, competitive ability, and reproduction (common measures of evolutionary fitness) in response to environmental exposures.

The investigators fed one group of mice a diet containing 25 percent of calories from a 1:1 mixture of fructose and glucose, the same ratio of sugars found in beverages and processed foods containing high fructose corn syrup. They fed a second group of mice a control diet in which the added sugars were replaced with cornstarch and fiber. Both groups of mice consumed their respective diets and lived in controlled environments for 26 weeks before entering the organismal performance assay, upon which all mice consumed the high-sugar diet. The researchers observed mice as they competed for territory, resources, and mates for 26 to 32 weeks.

Female mice fed a high sugar diet prior to entering the organismal performance assay were twice as likely to die than female mice fed a normal diet. Male mice fed a high sugar diet controlled 26 percent less territory and produced 25 percent less offspring compared to mice fed a normal diet prior to entering the organismal performance assay. A high-sugar diet increased fasting cholesterol levels and decreased glucose tolerance.

The authors concluded that a high sugar diet decreased survival, competitive ability, and reproduction in mice and led to metabolic dysfunction. This study was the first to use organismal performance assays in combination with an environmental intervention and the first to demonstrate the negative health effects of added sugars in mice at human-relevant doses.

• Link to full report.
• Learn about the effects of refined sugar on health in this episode of Found My Fitness podcast.