Glycemic Index Doesn't Tell The Whole Story:
Reducing Belly Fat Lipodystrophy
by Michael Mooney, December, 2007
Questions about using the Glycemic Index (GI) as a consistent way to determine what foods will cause an increase in fat in the belly have been detailed in recent years. For instance, the sugar fructose is a low glycemic sugar (carbohydrate) - eating it doesn't cause the rapid rise in blood sugar that would define it as a high glycemic carbohydrate - one that causes a significant rise in blood glucose. Fructose's glycemic index is 19, where table sugar's GI is 65 and the pure sugar called glucose's GI is 100. However, fructose decreases insulin sensitivity and readily converts to triglycerides (fats) which feeds central adiposity (a gain in belly fat) and raises blood triglycerides 1,2,3 which increases the risk of cardiovascular disease. If you use the Glycemic Index as the basis for your decisions, you might make the mistake of including fructose in what you allow into your body.
Too Much Carbohydrate Calories Increases Insulin Which Increases Fat Storage
Also realize that foods like pizza and ice cream have low glycemic indexes, but will promote belly fat increases and increase blood triglycerides significantly. Combining sources of high calorie carbohydrates, like wheat flour with the fat from cheese amplifies the fat storage effect that carbohydrates can stimulate.
This is true of pasta with cheese sauces, too, whether the pasta is whole wheat or not. There are many exceptions to the notion that Glycemic Index will consistently tell you what is best to eat.
While it is wiser to eat carbohydrate sources that are lower on the Glycemic Index scale, in general, the GI scale doesn't tell the whole story and can't be depended on, especially if the author of the GI diet you're considering doesn't understand how whole grain flour is very close to being as bad for bodyfat increases as white flour.
It's The Calories, Stupid
Any carbohydrate source will increase belly fat if the amount of carb calories it delivers are great enough to increase insulin. However, simply having too many calories increases belly fat, too. Agri-business would like people to think that whole grains are superior and healthy for everyone. Billions of dollars depend on you believing this notion, including money spent on studies that are meant to influence medical professionals, who then tell you to eat whole grains. To a very small extent whole grains do have an advantage - they contain fiber and tiny amounts of some essential nutrients. But for someone who has problems with belly fat (central adiposity), whole grains are basically almost as bad as white flour because of the large amount of carbohydrate calories they deliver, as is clearly detailed in the table below. These calories have to be stored somewhere and the first place your body places them is outside the portal vein of the liver, around your stomach and the organs in the visceral cavity. 4 This is an area of the body that is easily accessed -- it's close to the liver -- has lots of blood supply and contains very receptive fat cells, so the body uses this storage area first in its attempts at economical storage of excess calorie energy.
The chart below will help you determine what carbohydrate sources will feed belly fat the least and the most. (For more information, get the book Composition of Foods.) The more carbohydrate calories per pound a food delivers, the more that eating the food will promote increased belly fat. Note that this article only discusses carbohydrate calories, which can increase insulin production in the body, decrease insulin sensitivity and promote energy storage in the gut. It does not discuss fats or proteins. However, carbohydrates are the nutrient type that can directly increase insulin production significantly. Higher insulin levels that cause irregular insulin sensitivity cause disregulation of fat metabolism and fat storage.
As you see from the table, grains, whether whole or bleached deliver an extremely high amount of calories, far greater than green vegetables or fruits. And brown rice and white rice deliver similar amounts of calories. A diet to reduce belly fat would included lean meats/proteins, some healthy fats, and low calorie density carbohydrates, the ones in the table that give you the least amount of calories, certainly not grains, unless you were eating whole grain kernels, like the corn kernels in the table.
Also read my detailed article on this subject by clicking here.
1. Bantle, John, et al. "Effects of dietary fructose on plasma lipids in healthy subjects." American Journal of Clinical Nutrition
2. Elliott, Sharon, et al. "Fructose, weight gain, and the insulin resistance syndrome." American Journal of Clinical Nutrition 76.5 (2002): pages.
3. Teff, Karen, et al. "Dietary Fructose Reduces Circulating Insulin and Leptin, Attenuates Postprandial Suppression of Ghrelin, and Increases Triglycerides in Women." The Journal of Clinical Endocrinology & Metabolism 89.6 (2004): 2963-2972.
4. Björntorp, P. The regulation of adipose tissue distribution in humans. Int J Obes Relat Metab Disord (1996) 20(4):291-302.
Waistline Growth On High-Carb Diets Linked To Liver Gene
05 Dec 2007
Experts have been warning for years that foods loaded with high-fructose corn syrup and other processed carbohydrates are making us fatter. Now, a University of Wisconsin-Madison study has uncovered the genetic basis for why this is so.
Writing in the December issue of Cell Metabolism, a team led by biochemistry and nutritional sciences professor James Ntambi reports that a gene in the liver, called SCD-1, is what causes mice to gain weight on a diet laden with carbohydrates. The gene encodes the enzyme SCD, whose job is to synthesize fatty acids that are a major component of fat.
When the scientists fed a starch- and sugar-rich diet to mice lacking SCD-1 in the liver, the extra carbohydrates were broken down rather than being converted into fat and stored - keeping the mice skinny. Meanwhile, control mice with normal gene activity grew plump on the same food. "It looks like the SCD gene in the liver is responsible for causing weight gain in response to a high-carbohydrate diet, because when we take away the gene's activity the animals no longer gain the weight," says Ntambi. "These findings are telling us that the liver is a key tissue in mediating weight gain induced by excess carbohydrates."
The results could have implications for stemming the skyrocketing obesity problem in people, Ntambi adds. He explains that people pack on pounds in two ways, one of which is to eat extra fat, which then accumulates in adipose, or fat, tissue. But the main cause of weight gain is excess carbohydrates, because they trigger the body to produce new fat.
Blocking SCD's action in the liver could therefore offer another means to help people lose weight, Ntambi says, especially since obese people appear to have higher levels of the enzyme than do thin people.
"We think that obese individuals, in general, may have higher SCD activity in both the liver and in adipose tissue," he says. "So, they may have a higher capability of converting carbohydrate into fat."
High-carbohydrate diets have become exceedingly common not only in western nations but also in the developing world, as sugary ingredients like high-fructose corn syrup have crept into all sorts of processed foods, including soft drinks, baked goods, condiments - even supposedly healthy items like low-fat, fruit yogurt. What Ntambi's team has now demonstrated is how those diets can act directly on a gene to boost fat synthesis and storage.
"This is a very good example of a diet-gene interaction," he says.
The current study builds on previous work, in which Ntambi and his colleagues created mice that lacked SCD-1 everywhere in the body, including the liver, muscle, brain, pancreas and adipose tissue. No matter how much they ate, the mice didn't gain weight on either a high-fat or a high-carbohydrate diet. "But it was very difficult to tell which tissue was responsible for the effect," says Ntambi.
To tease this out, he and his colleagues subsequently bred mice that lacked SCD-1 in the liver only and placed them on either a high-fat diet or a high-carbohydrate, low-fat one. Much to their surprise, the mice on the high-fat diet gained weight just as quickly as normal, control mice.
"This suggests that in weight gain induced by a high-fat diet, other tissues beyond the liver are involved," says Ntambi.
In contrast, the mice stayed thin when they feasted on food heavy in starch and table sugar, or sucrose. They were also protected from the condition known as fatty liver. Ntambi thinks what's happening is that in the absence of SCD, the liver has no way to convert surplus carbohydrates into fat, causing the body to break them down instead.
The findings also highlight the central role of the enzyme and its main product, a fatty acid known as oleic acid, in overall carbohydrate metabolism, he adds. For example, mice lacking SCD could no longer make glucose - the sugar burned by cells for energy - leading to abnormally low blood sugar levels, or hypoglycemia. They also weren't able to make glycogen, a short-term storage form of glucose.
"It looks to us that if you don't have enough oleic acid - which the SCD enzyme makes - then the carbohydrate does not proceed through normal glucose metabolism," says Ntambi. As further evidence of this, when the scientists supplemented the mouse diets with oleic acid, normal metabolism was restored.
In both mice and people, on the other hand, eating lots of carbohydrate appears to boost SCD activity, leading to a glut of oleic acid, increased fat storage - and, over time, obesity.
"Too much carbohydrate is not good," says Ntambi. "That's basically what we are saying."
Ntambi's study was supported by the National Institutes of Health.
University of Wisconsin-Madison