Are low fat diets effective in weight loss?

Recent research and studies are finding that low fat diets are not very effective in weight loss. “Both cross-sectional and longitudinal analyses have failed to show a consistent association between diety fat and body fat” (1). Weight loss from low fat diets was found to be “modest and transient”, suggesting that other factors were more involved in the weight loss.

Americans are eating less fat but are gaining more weight

It’s shocking to see that 20% of children and over 33% of adults are considered significantly overweight in the United States (2). Most people associate gaining weight with eating high amounts of fat. Although this can be true, it’s been found that a lot of the low-fat foods that are also high in carbohydrates are the real cause of the increasing obesity rates. Over the past 3 decades Americans have been eating more and more calories, increasing their averages by over 500 calories a day. So what kind of food are they eating more of? Carbohydrates. A whopping 80% of these calories come from carbohydrates (3). But what about fatty foods? Surprisingly enough, Americans are eating less fat.

Americans have been consuming a lot less fat. It has decreased from 42% of our diets to only 34% (1). But yet obesity has been skyrocketing at all time highs. Fat isn’t the biggest problem, it’s foods high in carbohydrates that are low in fat and fiber. We are overrating and feeling excessive hunger do to our body getting too many carbs and not enough of other dietary nutrients. This is why low fat diets don’t have much success with weight loss. It doesn’t address the increasing rates that we are consuming foods with high glycemic indexes.

High Glycemic Index Foods linked to overeating

The Glycemic Index (GI) is a way to measure how foods containing carbohydrates impact our blood sugar. This does not mean that foods high in carbohydrates automatically have a high glycemic index, it takes other dietary factors into consideration. For example, pasta is very high in carbohydrates but ranks really low on the GI. On the other hand, most starchy foods like refined grain products and potatoes have a high GI.

Scientists are finding that foods with a high glycemic index are causing people to over eat. Consumption of high GI foods induces hormonal and metabolic changes that limit availability of metabolic fuels and lead to excessive hunger and overeating. Feeling hungry after these foods is due to our body attempting to restore energy homeostasis (1).

One study investigating this found that their obese subjects ate 81% more total energy (calories) after consuming two high GI meals (instant oatmeal) compared to them being fed two low GI meals with equivalent energy. This means that even food higher in fat but lower in the GI helped to make the patients feel fuller and reduced their chances of over eating.


Low Glycemic Index Foods

– 100% stone-ground whole wheat

– Steel cut oatmeal

– Pasta, barley

– Sweet potato, yam, pease, legumes

– Most fruits and carrots

Medium Glycemic Index Foods

– Whole wheat

– Brown rice

High Glycemic Index Foods

– White bread or bagels

– White rice, macaroni and cheese

– Pretzels, rice cakes, popcorn


Sources

1) http://pediatrics.aappublications.org/content/103/3/e26.full.ht

2) http://www.ncbi.nlm.nih.gov/pubmed/8022039?dopt=Abstract3

3) http://ajcn.nutrition.org/content/79/5/774.full

Additional Sources

– http://www.ncbi.nlm.nih.gov/pubmed/7743988?dopt=Abstract

http://www.diabetes.org/food-and-fitness/food/what-can-i-eat/understanding-carbohydrates/glycemic-index-and-diabetes.html?referrer=https://www.google.com/

– http://ajcn.nutrition.org/content/52/3/457.abstract?ijkey=b3fbb86991616c783e65b3003fbd09e947eed716&keytype2=tf_ipsecsha

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