Last updated on August 7th, 2011
Rodent health has never been a major concern of mine, but it seems to worry scientists a lot. For example, researchers at the University of North Carolina at Chapel Hill published a study in the journal Obesity that examines what happens to rats who are fed a snack-filled diet similar to that consumed by millions of Americans.
The study makes an important point about modeling human metabolic syndrome in lab rats, but it suggests even more.
The snack or “cafeteria” diet consisted of “high-salt, high-fat, low-fiber, energy dense foods such as cookies, chips, and processed meats.” The hypothesis was that rats who ate the cafeteria diet would better model human metabolic syndrome than rats who ate a lard-based high-fat diet.
Indeed, the study revealed that “rats fed human nutrient-poor foods [the cafeteria diet] develop severe metabolic syndrome which is more robust than the effect of traditional HFD [high-fat diet] exposure.” The rats on the cafeteria diet rapidly gained weight, and developed a “prediabetic condition with elevated glucose, insulin, and nonesterified fatty acids.”
The rats fed a high-fat diet did not gain significant weight compared to control groups fed either a low-fat or “standard chow” diet.
The high-fat fed animals “decreased food intake in terms of total grams to maintain caloric intake comparable to” the low-fat and standard-chow controls, but the cafeteria-fed animals “lacked this autoregulatory mechanism.” While the cafeteria and high-fat diets both have about 45–50% fat content, the cafeteria-fed rats ate about 40% more calories per day than the high-fat fed rats.
Sounds familiar, doesn’t it? Eat a carb-laden meal, and then get hungry again in an hour or two. Were the cafeteria-fed rats eating more carbohydrates than the high-fat fed rats? Yes. In their methods and procedures section, the researchers state that “fat intake was the largest macronutrient alteration in CAF [cafeteria-fed] rats, however, simple carbohydrate consumption was also elevated over HFD [high-fat] and SC [standard-chow] rats groups.”
So while the so-called high-fat rat diet may not have been “low carb” it was lower carb relative to the cafeteria diet. In considering their findings, the researchers seem to forget this point.
How do the researchers explain their findings? They don’t. They say there are too many possible culprits in the cafeteria diet to isolate one as the cause of over-eating. What are these possible culprits? The researchers identify them as an abundance of “sodium, saturated fatty acid, transfatty acids, and cholesterol” and a lack of “fiber and micronutrients such as vitamin A and calcium.”
A snack-based diet with cookies and chips would contain plenty of refined sugar and grain, and therefore plenty of carbohydrates, a fact the researchers acknowledge in their methods and procedures section. But in discussing their findings, the researchers do not even mention higher-carbohydrate content as a possible factor. Apparently, it’s not part of their paradigm, so they are blind to it.
The study was successful. Through it, the researchers confirmed their hypothesis that rats fed the cafeteria diet better mimic human metabolic syndrome and early on-set obesity than rats fed a lard-based high-fat diet. That finding by itself is suggestive.
But the rats they sacrificed could have showed them more.