Hadza People (07:36)

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There are biological needs for fat and fat cells are highly intelligent. Scientists study a hunter-gather tribe to understand why fat developed in humans. The Hadza do not have common health conditions in western societies.

Energy from Food (02:44)

The body stores energy from food as glucose and fat. Glucose only lasts a day while fat can last weeks. Humans evolved to store fat because it helps for survival and reproductive success.

Lipodystrophy (05:33)

This rare disease makes the body unable to store fat. In 1994, scientists discovered leptin, the hormone that regulates hunger and energy balance from food. Those with lipodystrophy cannot make leptin.

Leptin Gene Mutation (04:12)

A mutated leptin gene fails to regulate hunger by not telling the brain there is enough fat stored. If there is too little leptin the body goes into starvation mode. Those who lack leptin can take a leptin injection.

Role of Fat (05:11)

Fat is a complex hormone that serves different purposes throughout a person's life. Stored fat ensures there is enough energy for the brain to function. Fat creates estrogen and is important to bone health.

Fat Storage (01:38)

If fat is stored outside the abdomen and away from vital organs, it does not cause health issues. Exercise releases adiponectin, which guides fats in the blood to areas of safe storage.

Weight Regulation (06:49)

Scientists realize that the concept of calories in, calories out does not correlate with health. Each person's weight is regulated differently and has a healthy minimum. Making extreme changes in diet and exercise can harm the body if it is not maintained.

Genetics of Weight (03:18)

Studies of twins shows that weight, like height, is determined by genetics. Scientists have found more than 100 genes that play a role in determining weight.

Lack of Movement (05:00)

Obesity, which is based on the body mass index, has been rising in the United States and throughout the world. More than 100 diseases are linked to obesity. Researchers question whether lack of movement in modern society is the cause.

Types of Food (03:48)

Modern society has increased the amount of calories that are available on a daily basis. Some scientists believe how food is processed is the cause of obesity.

Treatments of Obesity (05:57)

Some scientists view obesity as a chronic disease that can be treated with a lifestyle plan. Moderate weight loss can have health benefits.

Credits: The Truth About Fat (01:11)

Credits: The Truth About Fat