Trans fat linked to obesity, type 2 diabetes mellitus

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By David Liu, PHD

Friday Sept 28, 2012 (foodconsumer.org) -- A new study in the journal of Obesity suggests that eating trans fat or trans fatty acids may increase risk of obesity and type 2 diabetes mellitus even if the calorie intake is not excessive. Both saturated fat and trans fat has early been proved in laboratory studies to be implicated in the development of type 2 diabetes mellitus.

Dietary intake of trans fat or trans fatty acids have been known to increase risk of heart disease.  According to Harvard scientists, more than 100,000 deaths from heart disease annually in the United States have something to do with dietary trans fat.

The current study, an animal trial of 42 male African green monkeys led by Kylie Kavanagh of Wake Forest University School of Medicine in Winston-Salem, NC and colleagues, found monkeys having had dietary intake of trans fat in a dose of about 8% of energy for six years gained significant amounts of weight with increased intra-abdominal fat deposition and impaired glucose metabolism.

Weight gain and insulin resistance or insensitivity can lead to obesity and type 2 diabetes mellitus, both are associated with increased risk of heart disease, the number killer in the United States.

Some previous studies have shown that trnas fatty acids may cause obesity and insulin resistance.  The researchers wanted to examine the effect of moderately high intake of dietary monounsaturated trans fatty acids on body weight and glucose metabolism.

For the study, monkeys were fed a diet with total calories that were to provide maintenance energy requirements without excessive energy to promote weight gain or obesity or type 2 diabetes mellitus.  

At six years of study, body weight and abdominal fat distribution was measured using computed tomography scan analysis.   A number metabolic parameters were also measured including fasting plasma insulin, blood sugar, and fructosamine concentrations.  Additionally, "postprandial insulin and glucose concentrations, insulin-stimulated serine/trheonine protein kinase, insulin receptor activation and tumor necrosis factor-alpha concentrations in subcutaneous fat and muscle were measured," according to the study report.

In addition to weight gain and impaired glucose metabolism, which were indicated by postprandial hyperinsulinemia, higher fructosamine, and tendency of getting higher glucose concentrations, the researchers also observed that "significant reduction in muscle Akt phosphorylation from the TFA-fed monkeys," which suggested "a mechanism for these changes in carbohydrate metabolism."

The researchers concluded "Under controlled feeding conditions, long-term TFA (trans fatty acids) consumption was an independent factor in weight gain. TFAs enhanced intra-abdominal deposition of fat, even in the absence of caloric excess, and were associated with insulin resistance, with evidence that there is impaired post-insulin receptor binding signal transduction."

This study suggests that eating trans fat can increase risk of obesity and type 2 diabetes mellitus.

One third of Americans live with obesity and about 25 million Americans live with type 2 diabetes mellitus.  Both medical conditions are associated with increased risk of heart disease, which is the number one killer in the United States, according to the Centers for Disease Control and Prevention.

Tran fat or commonly known as partially hydrogenated vegetable oils, which are made by a chemical process called hydrogenation, are commonly used in processed foods and restaurant-served foods.  Tran fat is also found naturally occurring in cows.  Trans fat can also be formed when cooking oil is subject to a high-heat treatment.

Human beings can't digest trans fat or trans fatty acids well and big chunks of trans fat can be situated across cellular membranes alternating the natural configurations and impairing the nutrient transportation in and out of cells, which leads to many medical conditions.

To reduce dietary intake of trans fat and thus reduce risk of obesity and type 2 diabetes mellitus, food consumers need to avoid or at least reduce intake of processed food and restaurant-served foods.

The Food and Drug Administration has required trans fat labeling for many years now, but it left a loophole to allow food processors to label any foods as "Zero trans fat" when a serving of the food contains no more than 0.5 grams of trans fat.  Because the size of serving is arbitrary, in reality, the FDA regulation allows food processors to label ALL foods as "Zero  Trans fat" foods.  Food consumers should check the ingredients list to see if any partially hydrogenated vegetable oil is used.

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