Humans Are Starch Eaters

Here’s an interesting talk by Nathaniel Dominy, PhD, an Associate Professor of Anthropology at Dartmouth University. He explains the central role of diet in the amazing worldwide success of the human species. If you can’t find enough to eat, you can’t do any of the other things that you would need to do to help you and your children survive.

He makes several important points. One is that human beings are behaviorally “plastic.” He uses the term “plastic” in the scientific sense, meaning that something can take any shape. Our behavior is “plastic” because it can easily be reshaped. As he pointed out, human beings can adapt to many different climates because we have learned to make and wear clothes. We can also learn to eat lots of different foods.

One type of food that is available everywhere except the Artic is starchy foods. All of the energy in our diet comes from sunlight, which green plants use to make glucose out of carbon dioxide and water. Plants then store a lot of this glucose in the form of starch, often in their roots or tubers and in their seeds. Unfortunately, starch is hard to digest. To digest it, we use amylase, an enzyme that converts the starch back to glucose.

Dominy suspects that our ancestors’ ability to recognize and use tuber-forming plants opened up a food source unknown to other primates. “It’s kind of a gold mine. All you have to do is dig it up.

Dominy points out that, when compared with other primates, human beings have extra copies of the gene for the starch-digesting enzyme amylase. As a result, we have a lot more amylase in our saliva than gorillas or chimpanzees do. People from societies that depend heavily on starchy diets have several more extra copies of the amylase gene and therefore produce a lot more amylase in their saliva. In other words, they have become genetically more efficient at digesting starches. This kind of change can be seen in genetically related populations that have been adapting to different diets for only a few thousand years.

Although humans can and do eat practically anything (we are behaviorally plastic), that doesn’t mean that we are well adapted to a meat-based diet. As he puts it, “Anatomically, we’re not adapted to meat at all…. We simply don’t have the adaptations that you would need to chew meat efficiently. Anyone can look at the teeth of their dog or cat and see what your teeth should look like if you’re going to eat meat. Our teeth don’t match.” Dominy concludes, “The fundamental component of the human diet is a mix of plant foods, with a large amount of starch coming from tubers and seeds.”

In this context, I’d point out that the adaptations to a meaty diet go far beyond the shape of the teeth. Even though dogs often eat a fatty, meaty diet, they generally don’t get high cholesterol or atherosclerosis unless they also have a thyroid disorder that upsets their cholesterol metabolism. In contrast, human beings that eat a fatty, meaty diet are much more susceptible than dogs are to high cholesterol and atherosclerosis. That explains why atherosclerosis is the leading cause of death in the United States but practically nonexistent in societies where people eat a low-fat, plant-based diet.


Type 2 Diabetes Keeps Fat People From Getting Even Fatter

Most people with type 2 diabetes are at least pleasantly plump, so why do so many severely obese people have no trouble with their blood sugar? I’ve known for decades that unexplained weight loss is a common sign of diabetes. A few years ago, I began to suspect that type 2 diabetes is what happens when one of the body’s natural defenses against further weight gain gets out of control. These suspicions were deepened when I realized that the drugs that are used to treat type 2 diabetes often cause weight gain as a side effect. The drugs are disabling the body’s natural resistance to further weight gain!

This interesting article from Endocrine Reviews argues that in type 2 diabetes, the problems with fat metabolism start long before the person starts having abnormal blood sugar levels. It explains how too much fat in the body and too much fat from the diet could end up causing type 2 diabetes. It explains how eating less and exercising more could solve the underlying problem.

The idea that type 2 diabetes starts off as a problem with fat metabolism makes a lot of sense. It helps to explain something that scientists have known since the 1930s: that you can cause insulin resistance in healthy volunteers by feeding them a high-fat diet for a week. You can restore their insulin sensitivity by feeding them a starchy diet for a week. A switch to a low-fat, high-fiber, high-carbohydrate, purely plant-based diet produces a dramatic improvement in people with type 2 diabetes, even before they have had a chance to lose much weight.

The traditional cure for type 2 diabetes was to eat less and exercise more. A more sensible approach is to start off by eating as much high-fiber, low-fat, plant-based food as you feel like eating. This kind of diet will rapidly correct your insulin resistance. As your insulin resistance improves, you’ll feel more like exercising.

Of course, if you have any major health problem or are taking prescription medications, you need to talk to a registered dietitian and your prescriber before making any major change in diet. You may need to have your dosages adjusted, and you may be able to stop taking some of your prescription medication.

Note: I explain this topic in more detail in my book Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2

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Photo by 95Berlin


Meat, But Not Sugar, Increased the Risk of Type 2 diabetes

Most of the people I talk to seem to think that they’d be healthier if they ate less carbohydrate. Most of them seem convinced that a high-carbohydrate diet makes people fat. They know that if you eat starch, it gets broken down into sugar. They know that when sugar flows into your bloodstream, your pancreas is supposed to release insulin to enable the sugar to enter your cells, where it can be burned for energy. That part’s true. However, they think that if you eat a lot of sugar or starch, you’ll somehow wear out your body’s ability to make or respond to insulin and thus you’ll end up diabetic. They couldn’t be more wrong. In reality, a high-carb, low-fat diet cures the most common type of diabetes.

If eating a starchy, low-fat diet made people fat and caused diabetes, then we’d see lots of fat, diabetic people in populations that eat a starchy, low-fat diet. We don’t. Instead, we see that the people of China and Japan, whose diet is based heavily on rice and vegetables, tend to be slim and remarkably free of diabetes and heart disease. We see the same thing in other populations that base their diets on other starchy staples. For example, the indigenous people of Peru eat a diet based heavily on potatoes. The Tarahumara of Mexico eat mainly corn and beans. The people in the New Guinea Highlands eat practically nothing but sweet potatoes. The story is the same wherever we look. In reality, the populations that eat low-fat, starchy, high-fiber diets are thin and healthy. The people who eat lots of fatty animal-based foods are the ones at risk for obesity, diabetes, and heart disease.

If eating a lot of sugar caused diabetes, then the people who eat the most sugar would be more likely than the average person to develop diabetes. On the contrary, a study of nearly 40,000 women age 45 and older in the United States found that the women who were eating the most sugar were no more likely to get diabetes than the ones who were eating the least sugar [1]. The women who were most likely to get diabetes were the ones who were eating the most meat! [2]

Reference List

  1. Janket SJ, Manson JE, Sesso H, Buring JE, Liu S. A prospective study of sugar intake and risk of type 2 diabetes in women. Diabetes Care 2003;26:1008-1015.
  2. Song Y, Manson JE, Buring JE, Liu S. A prospective study of red meat consumption and type 2 diabetes in middle-aged and elderly women: the women’s health study. Diabetes Care 2004;27:2108-2115.

For more information about diabetes, see my book Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2.

Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2


The Glycemic Index Won’t Help You Lose Weight

Lately, many nutrition gurus have been trying to tell me that eating a diet with a low glycemic index is the secret to losing weight. But if that were true, then carrots would be more fattening than fudge is.

Unfortunately, the glycemic index is being used to steer people away from the sort of food that can really help them lose weight and control their blood sugar: unrefined starches and vegetables. If you survey the world’s populations, you’ll find that the people who are eating diets based on unrefined starches and vegetables have low risks of obesity, heart disease, diabetes, and breast cancer—even though the glycemic index of their diet is high. In contrast, the people who are eating the most fat and protein—both of which tend to decrease the glycemic index of a meal—are the ones who are getting fat and sick.

The glycemic index was originally developed to fine-tune the system of carbohydrate exchanges that people with type 1 diabetes use to calculate how much insulin they will need to inject after a meal [1]. The glycemic index measures the effect that 50 grams of carbs from any given food has on your blood sugar. For example, if you ate 50 grams of carbohydrate from beans, your blood sugar wouldn’t go as high as if you ate 50 grams of carbohydrate from potatoes instead. In other words, beans have a lower glycemic index than potatoes do.

Like potatoes, carrots have a high glycemic index. However, you’d have to eat about 4 cups of shredded carrot to get 50 grams of carbohydrate. Thus, if you ate just one carrot, it would have only a small effect on your blood sugar. To correct for this problem, some people use the glycemic load, which is the glycemic index multiplied by the total amount of carbohydrate in the food.

The glycemic index and glycemic load are of surprisingly little value to dieters. One reason is that the glycemic index of any given food is so hard to predict. For example, you could increase the glycemic index of a potato by mashing it. Then, you could decrease the glycemic index of the mashed potato by adding milk and butter. Fats and proteins tend to decrease the glycemic index of a food. Although adding butter to a food decreases the food’s glycemic index, the butter does not make the food less fattening!

Even if you eat a meal that has a high glycemic load, that doesn’t mean that your blood sugar is going to go dangerously high. It all depends on your insulin sensitivity. People who habitually eat a low-fat, starchy diet tend to have much smaller blood sugar swings than people who eat a high-fat, low-carb diet. Scientists have known that fact since the 1930s! In fact, a diet based on high-glycemic-load vegetables and unrefined starches can restore the body’s insulin sensitivity, thus curing type 2 diabetes, within a matter of weeks.

Reference List

  1. Jenkins DJ, Wolever TM, Taylor RH et al. Glycemic index of foods: a physiological basis for carbohydrate exchange. Am J Clin Nutr 1981;34:362-366.

Note: For more information about the control of weight and blood sugar, see my book Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2.

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Thin Diabetes, Fat Diabetes

What’s in a name? A rose by any other name would smell as sweet. But when we are talking about diabetes, we should choose names that make sense. The French do. They use the term “thin diabetes” (diabète maigre) to refer to a catastrophic disease that results from failure of the pancreas. They use the term “fat diabetes” (diabète gras) to refer to a milder, curable cause of high blood sugar. Fat diabetes tends to occur in overweight people, and it’s made worse by fat in the diet.

When people talk about diabetes, they almost always mean diabetes mellitus, which is sometimes called sugar diabetes or just plain sugar. Diabetes insipidus is an unrelated condition in which the body can’t conserve water.

The most obvious symptom of untreated diabetes mellitus is excessive thirst and frequent urination. The word diabetes came from the Greek word for siphon, because water seemed to pass right through these patients. Their urine was loaded with sugar. Because they were losing calories through their urine, they tended to lose weight.

By the 1870s, doctors in France divided diabetes mellitus into two categories. Thin diabetes was a relatively rare but catastrophic, incurable disease that tended to happen in children and young adults who tended to be thin to begin with. These patients rapidly went into a coma and died, regardless of treatment. At autopsy, it was often clear that something had gone wrong with their pancreas. In contrast, fat diabetes was a common, relatively mild condition that tended to happen in middle-aged to elderly adults. It could be cured if the patient ate less and exercised more.

English-speaking doctors didn’t like the terms thin diabetes and fat diabetes. Instead, they used the terms juvenile diabetes and adult-onset diabetes. These terms are misleading because “juvenile” diabetes can strike adults, and “adult-onset” diabetes can occur in an overweight child. After the discovery of insulin in the 1920s, English-speaking doctors started to refer to thin diabetes as insulin-dependent diabetes mellitus and fat diabetes as non–insulin-dependent diabetes mellitus. People with thin diabetes would die without insulin therapy. In contrast, patients with fat diabetes often responded poorly to insulin therapy.

Now that so many people with fat diabetes are taking insulin, it’s confusing to refer to their condition as non–insulin-dependent. Instead, American and British doctors now refer to thin diabetes as type 1 diabetes. Fat diabetes is called type 2 diabetes. Unfortunately, these names are meaningless to the layman.

In the 1930s, a British researcher named H.P. Himsworth found that he could induce a condition that resembled fat diabetes in healthy volunteers by feeding them a high-fat diet for only a week. After a week of eating a high-fat diet, the volunteers were given a glucose tolerance test. This meant that they were given a dose of glucose in water and had their blood sugar measured every 15 minutes for several hours. When the volunteers had been eating a fatty diet for a week, they got a huge spike in blood sugar after drinking the glucose; but when they’d been eating a starchy, low-fat diet for a week, their blood sugar levels stayed low and stable after they drank the glucose. Himsworth’s review of these experiments was published in the British Medical Journal in 1940 [1].

When I talk to people who have fat diabetes, they typically don’t remember whether their diabetes is type 1 or type 2. Some of them have been taking insulin at least occasionally, so the term non–insulin-dependent makes no sense to them. Most of them have been told that they have to cut back on eating carbohydrates. Unfortunately, that means eating lots of protein and fat instead. Tragically, that also means that they are injuring their already damaged kidneys with the overload of waste products that come from burning protein for energy. It also means that they are probably making their insulin resistance worse, by eating too much fat.

One solution to this madness is to start using the term fat diabetes to refer to type 2 diabetes. The second solution is to shift the focus in the management of type 2 diabetes. Instead of telling patients to avoid eating carbohydrates to avoid blood sugar spikes, shouldn’t doctors be teaching their patients to shift to a low-fat, high-carbohydrate diet to restore their natural sensitivity to insulin? As the results of Himsworth’s studies suggested, clinical studies of a high-carbohydrate, low-fat diet have shown great success in helping people with fat diabetes shed pounds, control their blood sugar, and reduce or eliminate their need for prescription drugs [2,3].

One warning: If you have diabetes or any other health problem or are taking prescription medication, talk to a diabetes educator, registered dietitian, and your prescriber before making any major change in diet.

Reference List

1. Himsworth HP. Insulin deficiency and insulin inefficiency. Br Med J 1940;1:719-722.
2. Barnard ND, Cohen J, Jenkins DJ et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care 2006;29:1777-1783.
3. Barnard RJ, Jung T, Inkeles SB. Diet and exercise in the treatment of NIDDM. The need for early emphasis. Diabetes Care 1994;17:1469-1472.

Note: You can find more information about diabetes in my book Thin Diabetes, Fat Diabetes: Prevent Type 1, Cure Type 2.

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We’ve Known Since the 1930s: Fatty Diets Cause Insulin Resistance

This graph shows the glucose tolerance test results of a healthy person on a high-fat test diet as opposed to a high-carb diet. Notice that he had lower, more stable blood sugar levels after eating a high-carb diet!

Low-carb gurus have been telling people that insulin resistance, which is the underlying cause of type 2 diabetes, results from eating too much carbohydrate. Yet scientists have known since the 1930s that the problem can be provoked by a high-fat diet and reversed by a starchy, low-fat diet. You can read the research for yourself here.

This work was done in the 1930s. How long will it take before the low-carb gurus hear about it?


To Cure Obesity, “Eat Less Fat and More Starch”

Here’s an interesting article about the Pima Indians of Arizona.

For about 2000 years, the Pima had been growing corn, beans, and squash on irrigated land in Arizona. As a result, their traditional diet was high in starch and fiber and low in fat (~15% by calorie). After white settlers diverted the Pima’s irrigation water, the Pima had to fall back on the lard, sugar, and white flour supplied to them by the U.S. government. After World War II, the Pima adopted a diet that closely resembles the standard American diet. It is low in fiber and gets about 40% of its calories from fat. As a result, they have horrifically high rates of obesity and type 2 diabetes. In contrast, their blood relatives in Mexico who have kept more or less to their traditional diet have relatively low rates of obesity and diabetes.

Some low-carb gurus have tried to twist the Pima’s story into a justification for eating less carbohydrate and more fat. In reality, it provides strong encouragement for people to eat more starch and fiber and a lot less fat.