The connection between diets high in fat and obesity is well established. But a recent study at the Boston University School of Medicine found diets low in fat are also linked to obesity.

Children with a moderate intake of fat in their diets were the leanest of the children in the study of 106 families. Children with high fat diets were the most likely to be overweight but more interesting the children with low fat diets were also likely to be overweight.

Understanding what really makes us fat could be the most important health issue in the western world. In a press release on March 3rd this year the Centers for Disease Control in the United States predicted obesity would overtake smoking as the leading single cause of death in the next five years unless radical diet and lifestyle changes were made in the general population.

Many studies show that low fat diets may be less healthy than their original proponents would have us believe. Diets low in cholesterol, for example, consistently failed in repeated scientific research to improve the ratio of good cholesterol to bad cholesterol in the blood.

The resulting confusion over whether fat is healthy or unhealthy and what changes we really need to make to avoid excess body fat is simple enough to overcome once you understand how dietary fat affects your hormones.

Dietary fat can help you control your body weight in three main ways:

• Fat can make you feel full by stimulating the release of a hormone called cholecystokinin.
• Fat can reduce craving messages from your brain by slowing down the release of glucose into your bloodstream.
• Fat can also slow down the release of insulin, the “fat storage” hormone.

When you eat fat a hormone called cholycystokenin (CCK) is released. CCK sends signals to your brain that you’re full and you don’t need to eat any more. Obviously if you don’t feel hungry you’re less likely to overeat and put on weight.

Fat also slows down your digestion. Slowing down your digestion helps to regulate blood glucose supply especially to your brain. A more steady supply of glucose to your brain means less food cravings. Why?

When your brain is starved of glucose it sends out desperate messages to eat. We’re all familiar with poor mental functioning and the feeling of "loopiness" accompanying a lack of glucose in the brain.

Excess levels of glucose in your blood stimulate the release of excess insulin, the “fat storage” hormone. Remember fat helps slow down the release of glucose into your blood when you eat. So fat in your diet can also help control insulin.

How can insulin make you fat?

• Insulin stimulates a fat storage enzyme called lipoprotein lipase.
• Insulin inhibits a fat burning enzyme called hormone-sensitive lipase.

So by helping control blood glucose and insulin fat in your diet can indirectly reduce the storage of fat, encourage the burning of fat and reduce hunger. But before you start gorging yourself on every morsel of fat you see it’s important to understand the difference between “good” fats and “bad” fats.

Animal fats are implicated in many diseases including heart disease and obesity and should probably be classified as “bad” fats. Animal fats are solid at room temperature. When these more solid fats become part of your cell walls they can make those cell walls rigid. This rigidity can result in poor communication in your cells leading to excess insulin production and weight gain.

Worse still, the fat from red meat and egg yolks is high in arachadonic acid. Arachadonic acid is the major building block of a series of hormones called “bad” eicosanoids linked to most chronic diseases including heart disease, cancer, depression, arthritis and obesity.

To avoid these “bad” animal fats choose low fat sources of protein like chicken breast, turkey breast, tofu, whey protein isolate or fish.

Other sources of “bad” fats include the oil in deep fried food and most vegetable oils. These oils can slow down your body’s production of a series of hormones called “good” eicosanoids essential for your body’s healthy functioning. So avoiding deep fried foods and most vegetable oils is recommended.

“Good” fats are found in fatty fish like sardines and salmon, almonds, macadamia nuts, avocados and olive oil. These fats help make your cell membranes more fluid improving cellular communication, reducing insulin production and reducing your chance of putting on excess weight. The fat from fish or fish oil is particularly fluid and many studies have shown fish oil’s positive effect in the battle against many diseases.

So the basic recommendations for eating good fats to stay lean:

• Eat a modest quantity of good fats with every meal. Good choices include raw almonds, macadamia nuts, olive oil or avocados.
• Limit your consumption of egg yolks, red meat and sausages. In particular avoid the fat from red meat.
• Avoid deep fried foods and vegetable oils.
• Choose low fat sources of protein like turkey breast, chicken breast, tofu, whey protein isolate and fish.
• Especially increase your consumption of fatty fish like sardines and salmon and consider supplementing your diet with fish oil capsules.

The groundbreaking book Undersize Me has an illustrated chart of good and bad fats and outlines exactly the type and quantity of good fats you should eat for optimal health.

Undersize Me Book
The groundbreaking funny, fully illustrated book Undersize Me has a chart explaining simply which are good and bad fats. Undersize Me also gives exact directions on how much good fat to eat with each meal.
For more information on the Undersize Me book click here

Andrew Cavanagh is a professional health writer and speaker and a member of the Australasian Medical Writer's Association.

He is the author of “One hour to glorious health and permanent weight loss” and the groundbreaking “From depression to glorious health in six steps.” Both books can be downloaded free at this site.

Andrew Cavanagh is also the author of Health Watch, a weekly health feature for regional newspapers.

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