Ray's Take

Fiber is really cool.

What is fiber?

Non-digestible carbs (or difficult to digest).

They come from the cell wall of plants (pectins, mucilages, cellulose, hemicellulose, lignin are specific types of fiber)

There are two categories of fiber: soluble (can absorb water) and insoluble (stringy). Most veggies contain both.

Why is fiber cool?

It's cool bc it has metabolic benefits, and also obvious benefits.

What are the obvious benefits? (cool)

If you eat something (veggies) that is mostly water (90%+) and fiber (non-digestible), you are getting a high volume of food with very low calories (soluble fiber has 2 calories per gram. Insoluble has 0 cals). That's awesome bc it means you can eat as much veggies as you want. In fact the more you eat the better.

Fiber (bulk) and water also make you feel full. Obviously having more in your stomach will cause you to feel full and stop eating (technically through "stretch" receptors on our stomach and delayed gastric emptying).

What are the metabolic benefits? (very cool)

Lose weight, better insulin sensitivity (less diabetes), improved heart health, prevents colon cancer.

There is data that shows high fiber reduces risk of death.

How does it work? (very cool)

• When you eat fiber, the insoluble fiber forms a stringy net. The soluble fiber turns into a gel that covers the holes in the net.
• This gel filled net starts getting formed in the first part of the intestines (duodenum), which prevents the duodenum from absorbing simple carbs (sugar). This is good bc it dampens the sugar that goes into blood stream (which reduces insulin response) and also limits the amount of sugar that goes to the liver (which can get turned into fat).
• The carbs you eat travel further in your intestine, which is where your microbiome lives.
• These carbs feed the microbiome (important)/
• The microbiome also can feed on soluble fiber and turn it into short chain fatty acids.
• Short chain fatty acids improve insulin sensitivity, gut health, and also signal Peptide YY and GLP-1 (yes the same as the drug target) which make us feel full.
• Insoluble fiber can't be digested at all, so they travel all the way through the large intestine. It is theorized they can scrub off old cells from the intestine, thereby reducing risk of colon cancer. They also increase the speed going through the colon (which helps with constipation), but also reduces the time toxic compounds contact the colon.

TLDR

Eat more fiber.

The best way to do this is by eating veggies.

Sources

Barber TM, Kabisch S, Pfeiffer AFH, Weickert MO. The Health Benefits of Dietary Fibre. Nutrients. 2020 Oct 21;12(10):3209. doi: 10.3390/nu12103209. PMID: 33096647; PMCID: PMC7589116.

Ioniță-Mîndrican C-B, Ziani K, Mititelu M, Oprea E, Neacșu SM, Moroșan E, Dumitrescu D-E, Roșca AC, Drăgănescu D, Negrei C. Therapeutic Benefits and Dietary Restrictions of Fiber Intake: A State of the Art Review. Nutrients. 2022; 14(13):2641. https://doi.org/10.3390/nu14132641

https://robertlustig.com/fiber/

Amount of water and fiber, by vegetable