What Are Trans Fats & Why Are They Bad?

The FDA announced that a ban on trans fats in the next few years, but what are they and why are they so bad for us?

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Why Is the FDA Banning Trans Fats
Low-Fat Vs. Low-Fat: Which Diet is Better?

Two dietary reports released in the 1980s identified the reduction of dietary fat as the single most important change needed in order to improve Americans' health. As a result, the big trend in diets in the late 1980s and 1990s was to reduce or cut out fat of any kind. It seemed pretty simple: If you didn't want to get fat you shouldn't eat fat. The food industry responded by substituting sugars for fats in processed foods: many the "low fat" foods that hit shelves were lower in fat but higher in carbohydrates. In the early 2000s, diets like Atkins and the South Beach Diet had people focusing on reducing their carb intake with less concern about fat intake.

There are three main kinds of fats in our foods (saturated unsaturated, and trans fats) and each affect our bodies differently. Saturated fats have no double bond between molecules, so the lipid molecules are saturated with hydrogen. As a result, saturated fats are solid at room temperature (like butter and margarine), Unsaturated fats (like those in olive oil) have gaps between the hydrogen atoms and are liquids at room temperature. Companies can convert unsaturated, liquid fats into solids with a process called hydrogenation. Because they have to alter the hydrogen bonds to achieve this, these hydrogenated oils, are also known as trans fats.

Saturated animal fats were once thought to raise our LDL cholesterol (aka the "bad" cholesterol), and increase our risk of heart disease, so many companies switched to partially hydrogenated oils. Recent studies--like one in last year's Annals of Internal Medicine--found that saturated fat might not increase LDLs. Trans fats, however, not only cause increases in LDL cholesterol but also decreases HDL cholesterol (the "good" cholesterol). Studies have also shown high trans fats diets may cause memory loss, heart disease, and obesity.

Learn More:
Lipid Soluble Vitamins (Michigan State University Chemistry)
"The essential dietary substances called vitamins are commonly classified as "water soluble" or "fat soluble". Water soluble vitamins, such as vitamin C, are rapidly eliminated from the body and their dietary levels need to be relatively high."

The truth about fats: the good, the bad, and the in-between (Harvard University Health)
"For years, fat was a four-letter word. We were urged to banish it from our diets whenever possible. We switched to low-fat foods."

The Truth About Trans Fats (Live Science)
"Until 1983, if you ordered a fried goodie at a typical fast food joint, you'd get a crispy, golden product that had been fried in a vat of beef tallow or tropical oils, which are rich in saturated fat."

Why Are Animal Fats Solid Yet Vegetable Oils Liquid At Room Temperature? (Science Focus)
"Both fats and oils are molecules shaped like a capital E with a glycerol spine and arms made of fatty acid chains."

Did the Low-Fat Era Make Us Fat? (PBS)
"During the 1990s, the low-fat craze changed the way Americans eat, and yet they got fatter than ever. By 2001, one-third of the American population was overweight."