The nutrients that "everyone" knows about are very important to keeping you healthy and -- most importantly for dieters -- for controlling hunger.
But there are others that fewer people know of and many of them don't understand well that are just as important for controlling hunger.
Fiber is one of these.
Fiber it has no biochemical function because it never leaves the intestine, but it has an important physical function, and your body will trigger hunger or some other eating motivation when it needs more fiber to perform that function.
Fiber is indigestible plant material. Your body needs it and uses it as "bulk" to "push" biochemical waste out of your intestine.
This is very important for your health.
All by itself that "waste" is mildly toxic and harmful to your health. But more importantly, it provides an excellent home for bacteria and other things that can be extremely toxic and harmful to your health.
So your body naturally wants to get rid of it as fast as possible. Fiber is important for this and hence getting enough fiber is also important.
When your body senses that it is getting "constipated" (even if you can't feel it yet), it will tend to trigger hunger to try to stimulate you to eat something that will have the fiber it needs to end the constipation.
When this happens, you need to eat the right things.
For example, if you eat (e.g.) a bag of potato chips, you won't actually get much fiber; but you will get lots of Calories that will destroy your diet (if you happen to be on one); and you'll quickly get hungry again as your body keeps trying to make you give it what it really needs.
Conversely, however, if you eat vegetables, beans, high-fiber cereal, or other food with lots of fiber but not many Calories, you will get the fiber your body wants and "turn off" the hunger (if it was caused by a lack of fiber) without destroying your diet.
This the reason managing fiber (along with other nutritional factors that can have this same effect) is not optional if you are serious about losing weight.
We discuss this further in the rest of this section.
Keep it moving, folks, keep it moving.
J
The RDI of fiber is 20–30 grams/day. Over the years many researchers have suspected that dietary fiber can somehow help you lose weight. The threshold theory suggests that it does—though not exactly for the reasons most often discussed.
There have been a number of scientific hypotheses about how fiber might help people lose weight.
Perhaps it may help directly reduce food intake in some way.
Perhaps in some way it may cause less of the energy in food to be absorbed.
Perhaps it somehow stimulates “secondary metabolic activities” that affect the use of absorbed energy in some beneficial way.
In 1976 dietary fiber was defined as “plant polysaccharides and lignin resistant to digestion by the small intestinal enzymes of man”.
This means that what is called “fiber” is really a very “mixed bag” of different substances. “Different” may also mean different in physical properties as well as chemical ones. For example, fiber that typically has tiny particle sizes may have completely different effects in the intestine than fiber which stays in relatively large chunks—even if the two types are chemically identical.
One researcher has pointed out that the presence of fiber usually has secondary effects on other food components. For example, if you eat a diet high in fiber this often means that it is also higher in carbohydrates and lower in fat and sodium than low-fiber diets.
It is therefore also likely to be lower in “energy density” (carbohydrate has fewer Calories per gram than fat)—thus it will have a different effect than a low-fiber diet. However, in this case, the different effect is not a direct effect of the fiber on the body, but an effect of the fiber on other nutrients in the diet. (In this case, it displaces them.)
Experiments attempting to find out whether eating fiber reduces hunger and food intake have been inconclusive. Those that show there is an effect are contradicted by others that show no effect. Researchers believe that the weight of evidence demonstrates that fiber sometimes really does reduce hunger and eating behavior, but not always. The reasons for this are still speculative.
Experiments have been slightly more successful in finding out the effect of fiber on energy absorption. In general they have shown that fiber causes a small but measurable loss of energy because of non-digestion. In other words, on high fiber diets a small amount of the energy in food “passes through” without getting absorbed.
Unfortunately, it’s a very small amount—probably in the range of 30-180 Calories per day. Of course, as I’ve pointed out, over a period of time this amount of energy can put on considerable weight. Unfortunately, by this means alone, it would require just as long to take it off again.
Therefore, realistically, this effect of fiber is probably by itself too small to build a successful weight loss plan on. The beneficial effect is too easily overridden by even one “accidental” high-calorie meal. However, we dieters need every advantage we can get, and we are glad to see evidence that fiber can be even a small part of real weight loss.
Since fiber is never digested, it cannot be considered a “nutrient” in the normal sense. But since your body needs it to perform a vital internal cleansing function, it treats it just like a nutrient—i.e. it makes you hungry whenever it needs more. So we can probably call it a “proto-nutrient”.
The effect of fiber that dieters find most useful is its “regularizing” effect on the intestines. Eliminating what you don’t need is just as important to your health as getting enough of what you do need. Since hunger's main evolutionary focus is trying to manage food in order to keep you healthy, we are not surprised to find it taking an interest in foods that can help you eliminate that “stuff” that may cause disease.
Fiber prevents the constipation that was seen in virtually every VLCD research project. One respected VLCD researcher found that fiber not only reduced hunger but also made it more likely that people would actually be able to stay on the VLCD. These are exactly the effects that would be predicted by the threshold theory.
Fiber keeps the muscles of the intestine contracting smoothly and regularly rather than spasmodically and haphazardly. Since the sensation of hunger is itself partly a matter of the nature of the contractions of the intestines, it is wise to make sure the intestines don’t become “distressed” and arouse hunger to make you go eat some of that “high-fiber” chocolate cheesecake.
All this means that even though you may be tempted to think that fiber is “not so important”. Don’t! It is important! The body gets sneaky and tricks you into eating more when you aren’t eliminating properly. It knows you need dietary fiber and that you are a whole lot more likely to get it if you eat than if you don’t eat. (Duhh! Hunger isn’t smart, but it’s got that much figured out ).
This sneaky eating behavior often happens gradually and almost unnoticeably until you finally catch on that you’ve been eating more than you thought for several days—and then you’re likely to think it’s happening for some other reason. It can happen even after you’ve been doing the diet for a while and think you’ve mastered it. “Eternal vigilance is the price of freedom.”
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