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Role of Lipids in Obesity

Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

What makes us fat? In this lesson, we will explore the connection that lipids play in obesity and look at current research relating to obesity and lipids, as well as how obesity affects metabolism.

History of Fat and Obesity

You can go to the grocery store and see several products labeled 'fat-free', from 'fat-free ice cream' to 'fat-free gummy worms'. Often the public sees these products and thinks, 'Oh good! It is healthy!' But is it really? Are fat-free products actually good for us?

Fat free products are popular, from milk to candy
Fat free milk

Up until the start of this millennia, the prevailing theory in relation to obesity was that fats make us fat. In other words consuming fat, or lipids, is what was leading to the obesity problem in America. This idea stemmed from several observational studies that found that specific groups of people who consumed higher levels of fat had a higher body mass index. So, the correlation between fat intake and obesity led to the theory that fat intake causes obesity.

One of the prevailing theories was that fat consumption reduces our satiety (how full we feel). This is because fat is very calorie dense; 1 gram of fat gives 9 calories of energy to the body while 1 gram of protein or carbohydrates only gives 4 calories of energy. Thus, as we eat more fat, we have more energy that needs to be burned.

Hence, Americans started taking fat out of their diets. Diets focused on being low-fat and finding ways to take fat out of the diet. Marketing campaigns were focused on their food being fat-free or low fat.

But strangely enough, this didn't seem to help reduce the obesity problem. A few individuals saw progress with weight loss goals, but overall they weren't successful in the long term. When scientists started looking at a global scale, they realized that many cultures, such as the Greeks, had high-fat diets, but remained much skinnier than Americans.

So what was the answer? Today, scientists are getting a better picture of how fat affects our weight.

Current Research on Fat

When scientists started to realize that perhaps fat intake and obesity aren't directly correlated, new theories began to develop. Scientists have begun to understand that balance in the type of lipids consumed and the balance between fat, protein, and carbohydrates are important in losing and maintaining weight.

Our bodies can actually convert carbohydrates into fat very easily, so simply cutting out fat doesn't stop our body from making fat. Plus, consuming fat is important for our overall health. We need some fat in our diets in order to properly use and absorb some vitamins.

Focus on Fat Types

Current research on fat and obesity has focused on the effects of different types of fat and how fat plays a role in our overall health.

There are several different types of fat, from short chained to long chained and saturated to polyunsaturated. You've probably heard about omega-3 and omega-6 fatty acids. Current research shows that it is important to have a better balance between omega-3 and omega-6 fatty acids.

The exact ratio hasn't been determined, but most Americans consume around 20 times more omega-6 fatty acids than omega-3 fatty acids, which is probably way too many omega-6 fatty acids! This balance is what helps our bodies remain healthy and maintain a healthy weight.

Obesity and Lipid Metabolism

Another way to look at the connection between obesity and lipids is to see how obesity affects our lipid metabolism, or the way fat is used for energy. How obesity is originally caused isn't entirely understood, but scientists have been able to gain a better understanding of how obesity can lead to greater obesity.

In general, fat is useful. Our bodies metabolize lipids for energy. In a properly functioning metabolism, these free fatty acids are transported with albumin (a protein in the blood). Lipids are then broken down into energy in the muscles. Specific enzymes work to ensure a good balance between utilizing lipids for energy versus putting the lipids into storage.

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