Yesterday, a study hit the news that dietary fat, not sugar or carbs, is what causes weight gain and obesity. While this was a tightly controlled, randomized study, the subjects weren’t humans—they were mice. But that didn’t stop headlines like this: “Largest Study Of Its Kind Shows Eating Fat Is The Only Cause Of Weight Gain” from Tech Times, or “Study: Eating Fat Makes You Gain Weight” from Action News Jax. If you just read the headline, it all seems pretty certain, doesn’t it?
But can we look at studies on animals and say for certain that humans will react in the same way?
Animal studies can be useful in developing a question to be studied, or assist in gathering preliminary research on a topic. But animals are not people, so it’s important not to assume that the results in animals will be the same in humans. For example, a study on a new Parkinson’s or Alzheimer's medication tested in mice might generate headlines, but here's the problem--mice don’t get Parkinson’s or Alzheimer's. They are altered to exhibit some features of both diseases, but they don’t have the diseases. The drug may behave very differently in humans. In fact, most drugs that are successful in treating diseases in mice will fail when tested on humans. The same applies to studies that are conducted in test tubes—cells in test tubes are tightly controlled and not influenced by other systems in the body or environmental factors.
Studies on Saccharin (Sweet-n-Low) in the 1970's raised alerts on consumption of the low- calorie sweetener and the development of bladder cancer in rats. In fact, a health hazard warning was required on products with Saccharin. It wasn't until the 1990's that researchers figured out the link--proteins in male rat urine bound with saccharin, causing crystals to form in the bladder. This led to the development of bladder tumors. The issue with saccharin was specific to rats only--no such risk existed when saccharin was studied in humans.
So when you see a new study—particularly one with a sensational headline as noted above, take a moment to read the article. Was the study done on humans or mice? If it’s the latter, it’s interesting research to note, but it most likely won’t change recommendations, and shouldn’t change your daily habits.
So does eating fat make you fat, or is it carbs and sugar? While the mice might know the answer, we are still asking questions.