Losing weight and eating healthier top the lists of many Americans' New Year's resolutions. Now research shows how you diet may also help keep diabetes at bay. As this ScienCentral News video explains, it's new evidence in the battle against trans fat.
Chunky Monkeys
Trans fat, often used to fry fast foods, has been blamed for increasing obesity, heart disease and diabetes. Studies have shown that trans fat can raise levels of low-density lipoprotein (LDL), also known as "bad cholesterol," and decrease high-density lipoprotein (HDL), or "good cholesterol." This can lead to a higher risk of heart disease, one of the leading killers in the United States.
But Wake Forest University School of Medicine pathologist Kylie Kavanagh says that studies linking trans fat with diabetes have been less conclusive since studies in people are hard to control. "There was some evidence in some large studies that there might've been an association with diabetes," she says. "But the problem with looking at people and diabetes is that those people that ate trans fats also tended to eat snack foods, junk foods, other things that were high in sugar and fat."
WEB EXTRA: Kylie Kavanagh talks about why trans fats are in our food and tells us what to look for when we're at the supermarket.
To test only the effects of trans fat, Kavanagh fed male vervet monkeys a controlled diet for six years, the equivalent of 20 people years. While all the monkeys got the same amount of calories every day, half of them got food containing natural oils (like olive oil) while the other half had trans fat. "The two diets are identical in the way that they look, the way that they taste, there's no difference that you could have ascertained by eating, looking, or touching it," Kavanagh says.
Both diets, she says, would be equivalent to a typical "American diet," consisting of 35% of the calories coming from fat, 50% from carbohydrates, and 15% from protein. But she compares the trans fat diet to an American diet with more junk food. "This would be like a young, healthy 25- to 30-year-old man, eating once a day a fast food meal, a large fast food meal, and then throwing a couple cookies in throughout the day," she says.
The researchers found huge differences in the trans fat group after six years. Despite eating the same amount of total calories, they gained more than three times as much weight as the natural fat group. "They managed to gain weight even though they were on a diet," she says. The monkeys eating trans fat gained 7.2 percent of their original body weight, while the monkeys on the monounsaturated fat diet gained 1.8 percent.
CAT scans reveal that monkeys on the trans fat diet (top right) had more abdominal fat than those on the monounsaturated fat diet (bottom right).
CAT scans revealed most of that extra fat went straight to their bellies, a major risk factor for diabetes. "They had put 30 percent more of that weight gain around their middle section," Kavanagh says, "developing more of that apple shape, unhealthy body style."
Kavanagh's team also found troubling results when they drew blood samples from the monkeys. Those on the trans fat diet had higher blood sugar levels, which is typically a precursor to diabetes, Kavanagh says. "They also showed defects in the way that insulin works when it's released after you eat. Put together that they're also overweight and they have problems with glucose metabolism indicates that this diet is probably going to augment any predisposition that a person may have to develop diabetes, such as if they had a family history."
"So that young 25- to 30-year-old man," Kavanagh says, "by the time he's 50, is significantly larger around the middle, and significantly at higher risk for heart disease and diabetes."
Researchers are still unsure why trans fat is so different from natural fat and are researching why it redistributes fat around the abdomen. But Kavanagh says regardless of the mechanisms, she's always on the lookout for trans fat when she's at the supermarket. She advises consumers to check a product's nutrition label for trans fat, which is now listed on food packaging along with saturated fat.
She also says that you can check ingredient labels for phrases like "partially hydrogenated oil," which contain trans fat. "We don't really know what level of trans fat is safe to consume," she says, "but ... if you can remove them, you're not hurting yourself, and my feeling is that since it's not necessary in the food chain, why take the risk?"
Kavanagh jokes that she's been spreading the word about trans fat to her friends, even if public awareness is already pretty high. "Well, no one invites me to dinner! Everyone's kitchen I'm in, I'm poring through their shelves to read their labels and telling them that they shouldn't eat this or that." But she says her main message to them is: "If you're on a diet, these ingredients aren't helping you to lose weight, they're working against you."
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