One aspect of flexible dieting that is often overlooked by those critical to the approach is the importance placed by flexible dieters on hitting their daily requirement of dietary fibre.
What is Fibre?
Fibre is a type of carbohydrate that cannot be digested by our bodies’ enzymes. It’s the indigestible portion of food derived from plants such as cereals, fruits, vegetables, dried peas, nuts, lentils and grains. Fibre is grouped by its physical properties and has two main components, soluble and insoluble.
Soluble fibre, which dissolves in water, is readily fermented in the colon into gases and physiologically active by-products, and can be prebiotic and viscous.
Insoluble fibre, which does not dissolve in water, is metabolically inert and provides bulking, or it can be prebiotic and metabolically ferment in the large intestine. Bulking fibres absorb water as they move through the digestive system, easing defecation.
Plant sources of Fibre
Some plants contain significant amounts of soluble and insoluble fibre. For example, plums and prunes have a thick skin covering a juicy pulp. The skin is a source of insoluble fibre, whereas soluble fibre is in the pulp. Grapes also contain a fair amount of fibre.
Soluble fibre is found in varying quantities in all plant foods, including:
- legumes (peas, soybeans and other beans)
- oats, rye, chia, and barley
- some fruits (including figs, avocados, plums, prunes, berries, ripe bananas, and the skin of apples, quinces and pears)
- certain vegetables such as broccoli, carrots, and artichokes
- root tubers and root vegetables such as sweet potatoes and onions (skins of these are sources of insoluble fibre also)
- psyllium seed husks and flax seeds
- nuts, with almonds being the highest in dietary fibre
Sources of insoluble fibre include:
- whole grain foods
- wheat and corn bran
- legumes such as beans and peas
- nuts and seeds
- potato skins
- vegetables such as green beans, cauliflower, zucchini, celery
- some fruits including avocado, and unripe bananas
- the skins of some fruits, including kiwifruit, grapes and tomatoes
These are a few example forms of fibre that have been sold as supplements or food additives. These may be marketed to consumers for nutritional purposes, treatment of various gastrointestinal disorders, and for such possible health benefits as lowering cholesterol levels, reducing risk of colon cancer, and losing weight.
Soluble fibre supplements may be beneficial for alleviating symptoms of irritable bowel syndrome, such as diarrhoea or constipation and abdominal discomfort. Prebiotic soluble fibre products, like those containing inulin or oligosaccharides, may contribute to relief from inflammatory bowel disease, as in Crohn’s disease, ulcerative colitis, and Clostridium difficile, due in part to the short-chain fatty acids produced with subsequent anti-inflammatory actions upon the bowel. Fibre supplements may be effective in an overall dietary plan for managing irritable bowel syndrome by modification of food choices.
One insoluble fibre, resistant starch from high amylose corn, has been used as a supplement and may contribute to improving insulin sensitivity and glycaemic management as well as promoting regularity and possibly relief of diarrhoea. One preliminary finding indicates that resistant corn starch may reduce symptoms of ulcerative colitis.
Calculating Appropriate Fibre Consumption
How do we calculate our daily fibre requirement? The amount of fibre you require has a direct relationship to the total amount of calories you consume. On average, an intake of 10-13 grams of fibre per 1000 calories consumed is recommended. This is approximately 20-30 grams per day for an average of 2000-2800 calories per day. The average fibre intake in today’s diet is around 10-11 grams per day which is way below the suggested optimal range. Based on this data, most people would benefit from eating more fibre, as well as more fruit and vegetables in general.
The Benefits of Dietary Fibre
Fibre has several varied effects in the body which are relevant to overall health and body composition. Fibre is not an essential nutrient meaning you will not die if you don’t eat it regularly, but that doesn’t mean that a sufficient intake of dietary fibre isn’t good for you.
Some of the major effects of dietary fibre are as follows:
- Promotes fullness (satiety)
- Thermogenic properties of fibre
- Impaired nutrient absorption (absorb slightly less calories)
- Slows gastric emptying
- Improved glycaemic control
- Decreased blood cholesterol
- Decreased mineral absorption
- Impact on both fat cell metabolism and insulin sensitivity via fermentation to SCFA (short-chain fatty acids)
Fibre provides more volume in your food on fewer calories, so you get more bang for your buck when dieting. However, it’s important to note that fibre contains calories. Fibre has a caloric value to fibre of 1.5-2 calories per gram (depending on the food and fibre type). When tracking fibre, it’s best to include the tracked fibre into your daily requirement of carbohydrates. Best keep it simple.
When you track all your macronutrients and calories INCLUDING fibre, the way you eat tends to self-regulate. Put simply, if you hit optimal daily macros (protein, carbohydrates, fat, and fibre), with a sensible and moderate mindset, it generally means that at least 80% of your overall diet will consist of wholefoods, fruit and vegetables.