The best weight loss diet is a high fiber diet with a low calorie density

What exactly is the "fiber" in a high fiber diet? Years ago people called it roughage. It is the structural part of plants. Fiber is the part of our food that we cannot digest in our stomach or small intestine. It passes through them to the large intestine. Some animal foods, like a tough piece of steak, seem to be fibrous. They are not. No animal food contains fiber.

• Insoluble fiber absorbs water. It is like a sponge in our digestive tract. It swells up and fills our stomach. It helps move food through our intestines. 
  
  Some common sources of insoluble fiber are whole grains, vegetables, flax seeds, and the skins of some fruits.
  

• Soluble fiber dissolves in water in our stomach and forms a gel. The pectin we use to make jam or jelly is a soluble fiber. Soluble fiber lowers cholesterol levels by escorting cholesterol out of our body.
  
  When soluble fiber gets to the colon, bacteria in the colon make it ferment. For this reason, some scientists call it fermentable fiber. 
  
  The fermentation process gives off gases (beans contain lots of soluble fiber). Fermentation also produces some healthy short chain fatty acids that our body absorbs from the colon. 
  
  Some common sources of soluble fiber are oats, beans, vegetables, and the pulp of fruits. All plant foods contain both insoluble and soluble fiber, although some are better sources of one than the other.

A study published in the Journal of the American Dietetic Association found that:

• Thin people eat more fiber and carbohydrates than fat people do.

• Fat people eat more fat, saturated fat, and cholesterol than do thin people.

These results make it clear: thin people eat more plants and fat people eat more animal foods and oils. Voila! This study has discovered the perfect weight loss diet: a high fiber, low fat vegan diet.

And the perfect diet for making yourself fat is a diet full of meat, poultry, fish, eggs, dairy products, and oils. Hmmmm, that sounds like the diet that America has now exported to nearly every country in the world.

How does fiber help with weight loss?

• Fiber helps fill our stomach so we are satisfied before we eat too many calories.

• Our stomach empties more slowly when we are on a high fiber diet....so more time goes by before we get hungry again.

• Fiber slows down the absorption of carbohydrates. This means that glucose (sugar) is released into our bloodstream slowly over a period of hours. Our pancreas produces insulin slowly. We have time to burn our calories instead of storing them as fat. 

• One of the short chain fatty acids that we absorb from our colon is butyric acid. It goes through the liver and into the bloodstream. It tells the liver not to release too much glycogen for energy, so we can burn more fat instead. It also tells the pancreas not to produce too much insulin.

• Fiber blocks some calories so we don't absorb them at all.

• We actually have to chew high fiber foods before we can swallow them....what a novel thought. So, it takes longer to eat high fiber foods. A high fiber diet gives our hunger feedback system a chance to say "you've had enough" before we eat too many calories.

Americans take in 12 to 18 grams of fiber per day. The American Dietetic Association says we should increase it to at least 20 to 35 grams a day, depending on our calorie intake. 

But wait a minute. In African villages, where people eat lots of high fiber foods, they average 50 grams of fiber a day. Some people get as many as 80 grams, and they never get colon cancer. Now that is a true high fiber diet! If we eat only unprocessed whole plant foods, we can get as much fiber as the Africans. 

Some people worry that too much fiber in our diet will block our absorption of vitamins and minerals. There is no evidence for this if the fiber comes from whole plant foods. A high fiber diet is the natural diet for our species. In fact, fermentable (soluble) fiber actually improves our absorption of some nutrients, such as calcium.