Generally speaking, fiber is included under the category of low-calorie carbohydrates. But fiber is different enough to be considered a separate dietary carbohydrate component. Surprisingly, the question “What is the definition of fiber- what is considered fiber and what is not” is much more complex than most people would think.
If we are looking at fiber from physiological aspects, we have two main definitions:
Firstly, is the fiber soluble or insoluble.
Secondly, is the fiber fermentable or not fermentable.

Most people are familiar with the first definition, at least vaguely.
Soluble fiber “dissolves” in a liquid environment. A good example is guar gum: If you take a spoon-full of it and put it in water, it melts down and becomes some sort of gel.
Insoluble fiber,to the contrary, will not melt when mixed into a liquid.

As to the the second definition, some fiber is fermentable for example by bacteria in the intestine and turn into something else, such as fatty acids, methane and carbon dioxide. Other fiber is not fermentable, which means they will not turn into anything else.

What is the role of dietary fiber?
Fiber has several implications on the body, which are relevant to body composition health alike.
Although you will not die if you don’t consume fiber and it is not an essential component to your diet, it is still worth consuming it as it does wonders to both your body composition and health. Here are the physiological effects fiber has on your body:
1. It can make you feel fuller.
2. Slows down the gastrointestinal emptying process, or in other words – it can make you feel fuller FOR LONGER.
3. Reduction in the absorption of nutrients for better energy release.
4. Improved glycemic control, resulting from the slowdown in the process of emptying and reducing the absorption of nutrients.
5. Reduction in blood cholesterol levels.
6. Reduction in the absorption of minerals.
7. Affects Insulin sensitivity by fermentation and reversible fatty acids.
8. Effects on colorectal cancer.
9. Helps balancing the waste you expel from your body. Can help with both constipation and diarrhea.

 

These among else are some of the reasons our detox diet works extremely well as it’s vastly based on vegetables intake.

Satiety
One of the numerous signals fullness after, or during a meal is the level of tension of the stomach. High-volume foods are lot more likely to cause it than low-volume foods.
In this context, high-volume foods have lots of fiber relative to the low-calorie content. So they make you feel full even for both short long term. This means that people who start the day eating a salad, eat fewer calories during the day. This is because high-volume food and fiber filled them, so they ate less, but more calorie dense foods.
However, it should be noted that people find it difficult to meet their own calorie needs (athletes and “hard gainers ” who burn more than what they put it) should keep the salad at the end of the meal, and firstly eat all the high calorie food, so that they will not be filled too quickly.

Slowed gastrointestinal emptying
Soluble fiber tend to turn into a liquid gel-like material, and one of the results of the water-soluble fiber intake is the rate emptying of food from the stomach slows down when eaten. Overall, they create the material which causes the food do move downwards slower. Along with stretching the stomach, this tends to make people feel full for the long term as the food remains in the intestine for a longer period of time.

Slowing the absorption of nutrients
More results can be discussed in the context of soluble fiber is a delay in the absorption of food components – and this goes for carbohydrates, fats and proteins. Due to the gel-like solution created, enzymes joints can not reach other nutrients, so that more of them are carried outside the body. In other words, high-fiber diets will result in fewer calories absorbed.
It should be noted that the effect is of a large scale: fiber can reduce fat absorption by about 3% and protein by about 5%. There is not yet a measurable value for carbohydrates. For a more concrete example, an increased intake of 18-36 grams of fiber a day can lower your caloric absorption at 100 grams per day.
This can be either a good or a bad thing, depending on how you look at it. Anyone who wants to lose fat will not only feel fuller and eat less, but also will absorb less calories in the process.
On the other hand, for athletes and bodybuilders a diet which is high in fiber can be a terrible thing and undermine them in their goal. This is mainly because soluble fiber affect the absorption of protein. Also, for athletes with high calorie requirements, loss of calories caused by fiber intake probably is not recommended. Even if the effect is not large, it should still be taken into account.

Improved glycemic control
One of the best known and most discussed benefits of high fiber intake is improved control of blood glucose levels. In between the slowing down in emptying and reduction of carbohydrates digestion, soluble fiber tend to improve blood sugar levels. Instead of sharp bursts up (resulting from faster digestion), and dropping down, blood sugar levels stay balanced. While dropping down, the blood glucose can be another catalyst for hunger which is another effect on the control of hunger between meals (which is important especially during diets).

Reduction in blood cholesterol levels
An increased intake of fiber improves blood lipid levels. This is done through a variety of different mechanisms which are linked between themselves.

Reduction in the absorption of minerals
Dietary fiber can affect the absorption of minerals – especially calcium, magnesium, sodium and potassium. This usually is not a significant consideration, unless the above mineral intake is inadequate to begin with.
Also, when dietary fiber intake goes up (as opposed to supplements), there is an increase in levels of minerals which eliminates the effects of any issue that may arise. For example, in vegans the fiber intake is high (valued at about 100-150 grams a day), but there is no lack of nutrients. This is most likely due to the fact that the source of the fiber are fruits and vegetables, which high in fiber and other nutrients.
Conversely, when people start to add fiber in the form of supplements, problems begins to emerge. When it turned out bran lowers blood cholesterol levels, people began to consume huge quantities of it. But they did so from isolated sources, and not food. While it could actually reduce blood cholesterol levels, it was accompanied by mineral imbalances resulting from eating too much fiber that was accompanied by increasing intake of other nutrients.

Effects on insulin sensitivity through fatty acids fermentation
Some fiber can ferment and turn into other things, among them a short-chain fatty acids such as acetate, butyric acid and Frofinat. These are absorbed by the body and have a number of physiological effects. One is the effects on metabolism.
Short-chain fatty acids supplied by fermenting fiber, also affect cell metabolism and on insulin sensitivity; And while the short chain fatty acids these positive effect on insulin sensitivity, it seems that they do so by inhibiting the release of fatty acids from fat.

Effects on colorectal cancer
Consumption of fiber has physiological effects which can reduce the risk of colon cancer.

Aiding to expel the waste
Probably the most well known effect fiber consumption has is by helping to make “an easy exit”. It’s like nature’s broom. Fiber help to sweep everything from the intestine to the exit. This is done through several mechanisms.
First of all and foremost, increasing the speed of fiber crossing from one side of the colon to the other, so instead of sitting in the intestine the food moves towards the exit more quickly. Also contributing to the volume of pieces coming out, which in turn contributes to the adsorption of fluids, which makes the waste softer. Both these results contribute to a reduction in the time of transit and also contributes to better waste expelling habits.

Fiber and calorie balance
In relevance to body composition, fiber can contribute to caloric balance. As noted above, fiber affect caloric absorption (lowers it), in addition to feeling full (causing people to eat less spontaneously), improved blood glucose levels, cholesterol and other mechanisms. In general, the effect is that of reducing the amount of food consumed, and the lower absorption of calories, and thus to lose weight.

For anyone who is trying to lose weight, most of the effects of high-fiber intake are generally positive. Becoming less hungry, with stable blood sugar levels, and the ability to absorb fewer calories – these are a good outcome.
For those who are trying to raise their caloric intake, or gain weight, these exact same effects can be a bad outcome.

So how much fiber do we need?
As noted above, this is not a necessary dietary component. You will benefit from consuming fiber but you won’t die if you don’t eat fiber at all.
The American Dietetic Association recommends eating 10-13 grams of fiber per 1000 calories consumed. Ie 20-30 grams of fiber a day, for an average diet of 2000-3000 calories daily. It is worth mentioning that the average fiber intake is 10-11 grams per day, which is well below that. Most people should eat more fiber, but then again most people should include more fruits and vegetables in their diet anyway.
A diet which rich in fiber, especially from fruits and vegetables, also includes many other nutrients, so by looking at it only in terms of fiber intake can be misleading. Consumption of sufficient amounts of fruits and vegetables on a daily basis has many benefits beyond fiber intake. Including some fruit or vegetables at each meal is a good idea.

As with anything, moderation is key. Too little fiber is bad, too much fiber is also bad.
Find the balance yourself.
Depending on the frequency of the meals, somewhere between 5-10 grams of fiber per meal would be a good place to start. It should come to about 30-60 grams per day and cover the average requirements, without exaggeration.
Rapid increases in fiber intake might result in gas, so don’t jump ahead of yourself. Do it slowly and gradually so that your body can adjust to the new dietary component. Be aware of how your body reacts overtime to this new intake of fiber, whether you just started introducing it in your diet or if you are upping the intake.

What kind of fiber should you eat?
Well, really simply: If you eat enough fruits and vegetables on a daily basis, you will get a variety of fibers and cover your basic needs.
In certain situations, dietary fiber may play a role. For example, soluble fiber such as guar gum can be put into yogurt, protein powder, etc., to thicken or to provide a feeling of fullness. In other cases, many will use psyllium husks as a form of insoluble fiber if they suffer from constipation or similar problems.
However, for most people, it is recommended increasing fiber intake from food, not isolated supplements.