I really am compelled by this blog entry by Stephan Guyenet, in which he outlines all the reasons it is likely the carbohydrate hypothesis of weight gain is simply wrong, with a special eye on the premature insulinogenic theories of Gary Taubes.
Some excerpts:
'While we're on the subject, let's address the idea of "internal starvation". Taubes suggests that people overeat because they can't access their fat stores due to elevated insulin. However, obese people have equal or higher circulating free fatty acids and glucose (22, 23), so how is that possible? It's not. The internal starvation model was interesting at the time it was proposed, however the evidence has refuted it since then. If anything, obesity is a condition of "internal excess". This information is readily available in the scientific literature, and I'm sure the numerous obesity researchers he interviewed would have been happy to explain it to him, so it doesn't make sense that he instead relied on his own speculation here.
Let's also address the claim that obese people don't necessarily eat more than lean people. Food records are notoriously inaccurate, however there is at least one way to measure total energy intake in a precise and unbiased manner. It is called the "doubly labeled water method" (DLW). DLW studies have shown that after controlling for confounding factors, obese people almost invariably expend more, and consume more calories than lean people (24, 25). Weight stable obese people have a higher energy flux out of fat cells, and a higher metabolic rate, but it is not enough to overcome the higher calorie intake that is also observed (26, 27). That has been repeatedly confirmed and it is simply a fact at this point.
Therefore, the insulin hypothesis is not consistent with basic thermodynamics, and it's not consistent with research on the biological functions of insulin. Obese people do not have a defect in the ability to release fat from fat cells and burn it, to the contrary. They release more fat from fat cells than lean people, and burn more of it. However, this is compensated for by a higher energy intake, and a higher rate of fat incorporation into fat cells that counterbalances the increased expenditure. The fat cells of obese people do not suffer from excessive insulin signaling, to the contrary, the evidence suggests that their fat cells are insulin resistant and therefore insulin signaling is reduced. This shows that insulin does not cause obesity by acting directly on fat cells to cause fat storage. To understand obesity, we have to understand what causes increased food intake, and that factor is not insulin.'
Also:
I've already demonstrated that Taubes's conception of the effects of insulin are badly misguided, therefore it makes no sense to invoke insulin as a mechanism between carbohydrate consumption and body fatness, unless your hypothesis is that carbohydrate lowers body fatness by increasing insulin secretion.
Another problem with the hypothesis is a thing called the insulinogenic index (II). The II is simply a measure of how much eating a food increases insulin, per unit calorie (28). It turns out, it doesn't correspond with the carbohydrate content of the food very well. In particular, protein-rich foods such as beef can increase insulin secretion as much as certain starch foods such as pasta, or more. High-protein diets, as many of you know, aid with weight loss. The other problem is that refined and unrefined carbohydrates often have a similar II. Pasta made from white and whole-grain wheat have the same II, and the same goes for white and whole-grain bread (29). Doughnuts and cookies are on par with whole grain bread. So post-meal insulin is not a compelling explanation for the potentially different effects of protein, unrefined carbohydrate, refined carbohydrate and sugar on body fatness.
I think it's likely that refined carbohydrate and sugar can contribute to obesity, but by what mechanism? Insulin is not a compelling explanation. Food reward/palatability is an alternative possibility that fits the evidence better. Another plausible hypothesis is reduced fiber and micronutrient density.
Also:
Northern Cameroon, 1980s. The Massas tribe (also spelled Massa) is known for its overfeeding ritual called Guru Walla, which Taubes describes in GCBC:
The Massa tribe of northern Cameroon fattens their males using both milk and a porridge made from sorghum, a corn-like grain that provides sweet syrup from the stalk. One man gained seventy-five pounds on a ceremonial binge. The average weight gain tends to be fifteen to twenty pounds using milk and porridge. The Massa are cattle herders and their staple diet is primarily milk. This fattening comes about by the addition of carbohydrates (sorghum) almost exclusively.
Taubes states here that the typical diet is "primarily milk", therefore by inference, low in carbohydrate. Let's follow his reference and see what it says. It leads to a freely accessible paper by Drs. Igor de Garine and Georgius J.A. Koppert titled "Guru Fattening Sessions Among the Massa" (30). The Massas indeed herd cattle, but "their main use is not as food." The typical diet (not during overfeeding) is described as containing 516 grams of carbohydrate per day, and only 32 grams of fat (Table VIII). The typical diet is 81% carbohydrate, and primarily based on sorghum, according to Taubes's own reference. This account is consistent with other freely accessible references in respected peer-reviewed journals (31). These people are lean on their typical high-carbohydrate fare until they deliberately overconsume a mixture of sorghum and milk.
Most of Asia, 20th century. Many Asian countries, including China, Japan, Taiwan and India, have a traditional diet that is very high in carbohydrate. In many cases, the dominant carbohydrate was white rice, a refined carbohydrate. Yet traditional Japanese, Chinese and Southern Indians eating mostly white rice were renowned for their leanness. Any plausible hypothesis of obesity needs to account for these observations.
Kitava, 1990s. Dr. Staffan Lindeberg showed that the Kitavan diet is 69% carbohydrate, mostly from taro, breadfruit, sweet potatoes and cassava (32). Thus, their diet would have had a high glycemic load and high II. They also obtain 50 g/day of carbohydrate from fruit, most of which would presumably been sugar (unrefined). Yet there was no obesity on the island, and only a few individuals that were slightly overweight (33). Fasting serum insulin was low, consistent with other high-carbohydrate cultures. Dietary carbohydrate does not cause insulin resistance.
Pima, 20th century. The Pima of New Mexico currently have one of the highest obesity rates in the world, on par with Nauru. It is rather ironic that Taubes uses them as an example in GCBC, when they are at odds with his hypothesis. The Pima were first contacted in 1539 by the Spanish, who apparently found them to be lean and healthy. At the time, they were eating a high-carbohydrate, low-fat diet based on corn, beans, starchy squash, and a modest amount of gathered animal and plant foods from the forest and rivers in the area. In 1869, the Gila river went dry for the first time, and 1886 was the last year water flowed onto their land, due to upstream river diversion by settlers. They suffered famine, and were rescued by government rations consisting of white flour, sugar, lard, canned meats, salt and other canned and processed goods. They subsequently became obese and have remained that way ever since. Their diet consisted mostly of bread cooked in lard, sweetened beverages and canned goods, and they also received salt. More recently, their diet has modernized but still relies heavily on processed food (34, 35).
http://wholehealthso...esity.html#more
Edited by TheFountain, 19 August 2011 - 07:50 PM.
