What I do eat: the fiber factor

I do not count calories, but I do read nutrition labels and I pay attention to what I eat and how much.

Intermittent fasting does not require any particular diet on eating days, and the alternate day fasting that I do is, in principle, compatible with any diet. That’s one great thing about it. However, I do eat according to the same principles that motivate my diet, and this post lays out what those principles are and how I apply them.

What are those principles? Genetic studies in model organisms indicate that longevity and healthspan are improved when insulin (and insulin-like growth factor, or IGF) signaling is reduced. Insulin is induced by blood sugar, so reduced insulin signaling can be achieved by fasting, and by avoiding foods that raise blood sugar significantly. I also seek to improve insulin sensitivity so that less insulin will be produced. I have tremendous respect for the body’s many complex systems for telling me what would be good for it. The key here is to listen to what the body is telling me, which usually means eating food that I enjoy.

What do I look for?

Total. I do not attempt to count total calories consumed in a day or in a meal because I think that would be a fool’s errand. The uncertainty is simply too high, and errors accumulate throughout the day. A difference between calories consumed and calories burned sufficient for a dramatic weight change (in either direction) might be only 100 calories per day, much less than the likely difference between my best estimate and reality. But I don’t have to count calories because my body does it for me. I pay attention to hunger. I avoid eating when I’m not hungry, and I try to eat healthy foods when I am hungry. Also, if there is a nutrition label, I look at total calories, and I try to estimate calories when there isn’t a nutrition label. Even though I’m not keeping a total, I ask myself whether I would rather have this food or more of the alternative. The amount that I’m likely to eat each day amounts to a budget, and I’m deciding where to allocate those available calories.  I also keep a log of what I eat each day. It’s not terribly detailed. I just write it down quickly (usually without a lot of detail).

Fat and alcohol. I’m generally neutral on fat, but it’s complex, and much of the science is controversial. While some fats are clearly toxic (e.g. trans fats), others are likely to be healthy (e.g. fish oils). It also seems clear that dietary fat is less likely to lead to body fat than dietary carbohydrates, and there are many nutritionists (the LCHF, low carbohydrate, high fat, school) who recommend a high fat diet. Furthermore, eating more fat generally leads to eating fewer carbohydrates, which is better for reducing blood sugar. What’s more important to my diet is that fats (and alcohol) consumed at a meal with carbohydrates can mitigate the effect of the carbohydrates on blood sugar.

On the other hand, fat is extremely high in calories; when researchers want mice that are obese, diabetic and dying of coronary artery disease, they feed the mice a high fat diet, and it works. So, I try to focus on healthier fats (olive oil, fish and fresh nuts), and I avoid trans fats completely, but I don’t worry too much about the fat in cream, butter, eggs or chocolates if it enhances my enjoyment of food.

Carbohydrates and added sugar. Since my goal is to reduce the glycemic response to food (spikes in blood sugar), I try to eat a low carbohydrate diet and avoid added sugar as much as possible. Ideally, that would mean little or no sugar. However, many foods that I truly enjoy (fruits such as blueberries and peaches, chocolates, custards, shortbread) have significant sugar, and I let myself enjoy them in moderation. I completely avoid sweetened drinks, and overly sweet foods, of all kinds. This includes artificially sweetened drinks; a preference for overly sweet food is a taste that I do not wish to acquire.  

Fiber. A diet high in fiber reduces the effect of carbohydrates on blood sugar, and generally improves insulin sensitivity. Fiber is the primary factor in maintaining a healthy gut microbiome, and many epidemiological studies find that people, and populations, that eat more fiber are healthier and live longer. So, I try to eat foods that are high in a variety of fiber, particularly vegetables, whole grains and some nuts.  I also consult nutrition labels when they are available. When I do I always calculate what I call the fiber factor, which is a ratio between the percent of daily value (%DV) for fiber compared to %DV for total carbohydrate.

Fiber factor = (% DV dietary fiber)/(% DV total carbohydrate)

        = ((g. fiber)/(g. total carbohydrate)) x 12

Higher is better. The maximum possible value is 12, which is what you would get if all of the carbohydrates in the food were from fiber.

For example, if the label lists:

Total Carbohydrate    8 g.    3%

Dietary fiber               2 g.     8%

the first formula gives 8%/3% = 3.67 while the second gives (2 g. / 8 g.) x 12 = 3. The difference between these results is rounding error. The second formula is slightly more accurate, but the difference between the two values is not so great that you should worry about it.

Fiber factor is completely independent of serving size (no need to count calories).

If you find it tedious to do arithmetic in your head while standing in the grocery aisle, just compare the two values.  You want the %DV for fiber to be higher than the %DV for total carbohydrate.

Most legumes have a fiber factor about 4. Nuts have a fiber factor in the range of 6 to 8.  Where the fiber factor is most useful is when assessing cereals, grains and vegetables, because there is a lot of variation.

The following table is informative:

Cereal	Fiber factor		Fruit or juice	Fiber factor
Nature’s Path Flax Plus	2.0		Oranges	3.0
Oatmeal (no sugar)	1.7		Orange juice	0.0
Oatmeal (usual sugar)	1.0		Apples	2.1
Nut and honey granola	1.5		Apple sauce	0.8 to 1.4
Cheerios	1.4		Apple juice	0.2
Frosted Mini Wheats	1.3		Strawberries	2.7
Honey Bunches of Oats	1.1		Blueberries	1.7
Corn Flakes	0.4		Prunes	1.3
Frosted Flakes	0.2		Dates	1.3
Special K	0.1		Peaches	1.0

I look for cereals with a fiber factor close to 2. They are hard to find. Fruits reliably have a fiber factor over 2, but juices typically have a fiber factor of 0. Fiber is lost upon juicing. I have stopped drinking fruit juices altogether.  A really striking case is carrot juice. Carrots have a fiber factor of 3, but the juice has a fiber factor of 0.

Fiber is lost when juice is made from fruits or vegetables. Here we can calculate that carrots have a fiber factor of three but carrot juice has a fiber factor of zero.

Bread or grain	Fiber factor		Vegetable	Fiber factor
Whole grain bread	1.2 to 2.0		Green beans	6.0
Brown rice	1.7		Broccoli	5.0
White rice	0.7		Lettuce	3.0
Hearty crispbread	2.0		Carrots	3.0
Rye bread	0.5 to 1.2		Tomatoes	3.8
Pasta	0.5 to 1.2		Kale	2.3
Sourdough bread	0.2 to 0.6		Corn	1.7
White bread	0.2 to 0.6		Potatoes	1.5

Once I started looking at fiber factor I noticed some surprising things. Some chocolates have a fiber factor as high as 3.6 while others (most) have a fiber factor of 0. The list of ingredients is invariant: cocoa liquor, sugar and cocoa butter, in that order. What varies is how much fiber is retained during the processing of cocoa to make the liquor. What really interests me is that the specific chocolates with high fiber factors are the highest quality (at least, they are the ones that I prefer).  I’ve used this to identify some great chocolate that I would not otherwise have purchased. The best chocolates are also the healthiest. It’s a win-win situation!

Good chocolates can have a fiber factor of 3 or 4, while most chocolates have a fiber factor of zero.

Postscript: I am aware that when the FDA changes its daily value of fiber from 25 g to 28 g, the fiber factor calculated by the two formulae will diverge by that factor (25/28). Fiber factors calculated using the new % DV will be about 90% of the values calculated by the formula using grams.  I don’t think this difference matters that much, because %DV values are often rounded off by at least 10%. So, I will stick with the existing formula based on grams because it is easier to calculate using 12 than 10.71.

Fiber factor = ((g. fiber)/(g. total carbohydrate)) x 12

What matters is that higher fiber factors are better. That always works!