The Musical Fiber Diet

I tell you, we are here on Earth to fart around, and don’t let anybody tell you different.
— Kurt Vonnegut.

When I started to do research on fiber in diets, I quickly found that dietitians drone on and on about three sources of calories in your diet: carbs, protein and fat. Fiber is indigestible, so it is excluded. The resulting triumvirate of nutrients is all you need in order to define any particular diet. Or is it? The truth, as usual, is messier than that, but could be a life-saver. At the risk of making you think about pie, let’s start by looking at a typical American low-fat diet:

Low-fat American diet with no fiber

The amount of protein in your diet is the least flexible of the three food groups. Too little, and your blood vessels leak. You start to swell up like a water balloon. Unlike fats and carbs, a certain amount of protein is essential in your diet. We know those actual amounts thanks to chicken and pig studies. It turns out that it’s difficult to recruit humans – even college students – for starvation studies. That means much of what we know is extrapolated from farmers, who are always trying to minimize the amount of expensive protein they feed their animals. It’s far cheaper to fatten them up on carbs. That, um, applies to people, too.

It turns out that the minimum percentage of protein in the diet holds steady across most animals.  So, humbling as it may be, a pig’s lower limit is probably a good proxy for humans, at 15% of dietary calories.

Ammonia comes out where?

On the other hand, too much protein can put a strain on your kidneys and liver. The upper limit is harder to nail down, but when it exceeds the ability of your liver to process it and your kidneys to excrete it, your urine backs up into your blood, you become slightly green and you begin to pee ammonia. Sure, you might be able to wash windows with that, but it’s not good for you in the long run. You typically don’t reach that point until your protein intake exceeds around 35% of your calories. Depending on your overall calorie intake, that’s about 170 grams of protein, or 3 half-pound burgers a day. If you think about it, that’s just a snack for someone like Michael Phelps, which demonstrates that the amount of protein you can tolerate is also related to how crazy physical you are. Here are some sample diet plans, sorted by protein percentages, so you can see how wide the range is:

Diet Plan protein (%)
carbs (%)
fat (%)
American 15 65 20
Paleo 20 20 60
Moderate 25 50 25
Low-fat 25 60 15
Atkins 30 5 65
Zone 30 40 30
Low-carb 40 25 35
Ketogenic 45 10 45
P90X 50 30 20

The typical American diet has the least amount of protein, in favor of the highest carbs. Despite its macho meat-shredding image, America seems far happier with French fries and Twinkies. At the high end is P90X, a muscle-builder’s diet that calls for a heroic amount of protein. If you’re not pumping iron, this diet could turn you green.

The rest of us, according to more sober dietary recommendations, should constrain our protein to a fairly narrow range between 20% and 30%. For the sake of argument, let’s go with the average: 25%. But when we do, we run into several interesting problems.

Hope you like fat

The pie chart at the start of this article is for the low-fat diet that has successfully guided Americans to the greatest epidemic of obesity of all time. Switch to a low-carb diet with the same amount of protein, and you get this juicy fat pie:

low-carb diet

To lower carbs you have to increase fat, because we’re holding the protein at 25%. According to this analysis there are really only two parts of your diet that you have any control over, and lowering one will always raise the other. A low-fat diet implies a high-carb diet, which doesn’t sound nearly as healthy. Similarly, a low-carb diet is actually a high-fat diet, which sounds even less appealing. But the fact is, reducing one part of the triad inevitably raises another. So we’re doomed, right?

Well, of course we’re doomed. No one gets out of here alive. But in fact, this particular pie is only half-baked.

When do we get to the fiber?

One problem with this simple picture is that there are other sources of calories besides the big three. One that is dear to my heart is alcohol. My doctor says it is also good for my heart, although I had to go through a lot of doctors to find her. Alcohol is a source of calories, too. Unlike carbs and fats, though, alcohol is digested by the liver, which squeezes 7 calories out of each gram. So our pie really has four slices, not three. But before I cook up a new pie chart, we need to introduce another source of calories: fiber. Yes, fiber is considered to be indigestible, but that just means that your unaided gut can’t break it down. However, the bustling bacteria camping out in your bowels just love the stuff. Because you don’t digest it, the fiber makes it intact all the way to your colon, where your microbes eagerly feast on it. In doing so, they actually create fatty acids that – you guessed it – have calories after all. So fiber becomes the fifth slice of the pie. Here’s the pie chart for the final accounting, assuming a “moderate” diet:

nutrients by calorie

The fatty acids derived from fiber include something called butyric acid, which turns out to do marvelous things in your colon, such as thickening its lining, improving the mucus barrier and reducing inflammation. This is largely the work of bifidobacteria, which is a welcome bug to harbor in your gut, even if butyric acid stinks like rancid butter. People who eat fiber have far less GI inflammation, which means fewer episodes of irritable bowel syndrome and a lowered chance of getting colon cancer. As if that isn’t enough, it can lower your cholesterol and reduce your chances of getting type 2 diabetes, all as a consequence of bifidobacteria digesting “indigestible” fiber. In particular, bifido, as we call him around the house, likes inulin, a fiber found in veggies like Jerusalem artichokes, onions and chicory root.

This conversation goes south

Of course, there is the indelicate matter of gas that we must attend to. Those bacteria produce more than fatty acids, and that’s why adding fiber can be called a musical diet. You may not be surprised to learn that a primo source of fiber is beans. Most of the fiber you eat is either vegetable or fruitish in origin, because meat doesn’t have any fiber to speak of. For your amusement (or pun-ishment), I have assembled a short but perhaps memorable list of the vegetootles that may add some music to your day, including fartichokes, marshrooms, asparagas, bleets, patooto skins, bell poopers, and, of course, leeks. There are many more, but I couldn’t make funny words out of them. The Mayo clinic has a good list of them here:

If you have to pick a gas to pass, choose hydrogen or carbon dioxide. They’ll have you tooting like a motorboat, which is fairly humorous, but not eye-watering. However, the bacteria that produce hydrogen sulfide can really clear the room. Although we know of no one who has actually been killed by hydrogen sulfide toots, we still refer to them as deadly. And don’t forget methane, which can turn your butt into a flamethrower if you light it. Many a frat house has been scorched this way. For some reason, probably related to decorum and civility, sorority houses are not similarly afflicted. Rest assured, women fart as much as men, but they may be more convincing when they blame the dog.

What’s wrong with these charts?

But wait! The chart above shows you the percentages of the five food groups by calorie. To make any sense of that, you need to know how that relates to real-world stuff like weight. How much does a calorie’s worth of food weigh? That depends on its energy density; for instance there are 9 calories per gram of fat, but only 2 calories per gram of fiber. When you take that into account, you have to slice the pie differently:

nutrients by weight

That big chunk of fat gets reduced to a modest slice, and the amount of fiber greatly expands. This is a better way to view the data; to truly visualize the balance of nutrients in your diet, you need to see actual quantities of food, not just abstract calories. When you look at the proportions based on the actual serving size, you realize that you probably aren’t eating enough fiber. Sadly, we may be drinking too much as well.

The moral of this story is that fiber is good for you and should be a bigger part of your diet. It is healthy for your colon and it provides bulk to stave off hunger pains. It lowers cholesterol and prevents type 2 diabetes. Taking fiber out of our diets with foods like white bread and refined sweets is a big contributor to the obesity plague. We need to figure out good ways of incorporating more fiber into each meal. A good start is to avoid processed food, which is like livestock feed: a modicum of protein and a bunch of cheap carbs. And add some veggies to your diet. I know, your mom told you that. The thing is, she was right.

So, even though it comes with a little musical accompaniment, that’s the way it goes. Fiber is neglected, but essential. You’ll just have to poot up with it.


In my research for this article, I discovered that farting is one of the few biological functions that continue after death. You may be gone, but the microbes in your gut can party on for hours, dancing with tiny lampshades on their heads, long after the lights have been turned off. It gives the phrase “party-pooper” a whole new meaning. I know, it’s gross and irrelevant, and yet it seemed important to bring it up.


Crampton, E. W. “Nutrient-to-Calorie Ratios in Applied Nutrition.” The Journal of Nutrition 82, no. 3 (March 1, 1964): 353–365.

Anderson, James W, Pat Baird, Richard H Davis Jr, Stefanie Ferreri, Mary Knudtson, Ashraf Koraym, Valerie Waters, and Christine L Williams. “Health Benefits of Dietary Fiber.” Nutrition Reviews 67, no. 4 (2009): 188–205. doi:10.1111/j.1753-4887.2009.00189.x.

Jh, Cummings, Bingham Sa, Heaton Kw, and Eastwood Ma. “Fecal Weight, Colon Cancer Risk, and Dietary Intake of Nonstarch Polysaccharides (dietary Fiber).” Gastroenterology 103, no. 6 (December 1992): 1783–1789.

Salmerón, Jorge, Alberto Ascherio, Eric B. Rimm, Graham A. Colditz, Donna Spiegelman, David J. Jenkins, Meir J. Stampfer, Alvin L. Wing, and Walter C. Willett. “Dietary Fiber, Glycemic Load, and Risk of NIDDM in Men.” Diabetes Care 20, no. 4 (April 1, 1997): 545–550. doi:10.2337/diacare.20.4.545.

Brown, Lisa, Bernard Rosner, Walter W. Willett, and Frank M. Sacks. “Cholesterol-lowering Effects of Dietary Fiber: a Meta-analysis.” The American Journal of Clinical Nutrition 69, no. 1 (January 1, 1999): 30–42.

Kumar, Chethan M, Kollegal S Rachappaji, Chilkunda D Nandini, Kari Sambaiah, and Paramahans V Salimath. “Modulatory Effect of Butyric Acid—a Product of Dietary Fiber Fermentation in Experimentally Induced Diabetic Rats.” The Journal of Nutritional Biochemistry 13, no. 9 (September 2002): 522–527. doi:10.1016/S0955-2863(02)00180-8.

Spiller, R. “Review Article: Probiotics and Prebiotics in Irritable Bowel Syndrome.” Alimentary Pharmacology & Therapeutics 28, no. 4 (August 15, 2008): 385–396. doi:10.1111/j.1365-2036.2008.03750.x.

Hague, A., A. M. Manning, K. A. Hanlon, D. Hart, C. Paraskeva, and L. I. Huschtscha. “Sodium Butyrate Induces Apoptosis in Human Colonic Tumour Cell Lines in a P53-independent Pathway: Implications for the Possible Role of Dietary Fibre in the Prevention of Large-bowel Cancer.” International Journal of Cancer 55, no. 3 (1993): 498–505. doi:10.1002/ijc.2910550329.

Osman, Nadia, Diya Adawi, Göran Molin, Siv Ahrne, Anna Berggren, and Bengt Jeppsson. “Bifidobacterium Infantis Strains with and Without a Combination of Oligofructose and Inulin (OFI) Attenuate Inflammation in DSS-induced Colitis in Rats.” BMC Gastroenterology 6, no. 1 (December 1, 2006): 1–10. doi:10.1186/1471-230X-6-31.

Brown, Lisa, Bernard Rosner, Walter W. Willett, and Frank M. Sacks. “Cholesterol-lowering Effects of Dietary Fiber: a Meta-analysis.” The American Journal of Clinical Nutrition 69, no. 1 (January 1, 1999): 30–42.