Saturday, September 4, 2010

Metabolism of Low Carb

Dr. Eades might be too smart for his own good, but I've learned a ton from his blog.  This is a really simple way to better understand why low carb consumption is good for you - plain and simple, it is because of blood sugar control.
"Finally, I can't understand why the instructions to the low-carb group were to increase carbs to 120 grams per day after the initial two month induction. We don't know how many carbs the subjects in this study were actually consuming because the data shows carbohydrate intake only as the percent of total energy intake, but without showing what total energy intake is. If we assume that the subjects were eating about 120 grams per day, we know that they were right on the cusp of having any advantage from the low-carbohydrate diet other than the spontaneous caloric restriction it brings about. Our bodies need about 200 grams of glucose per day for all the tissues requiring sugar for proper function. Under conditions of zero carb intake, the body replaces about 70 grams of this glucose with ketone bodies, leaving about 130 grams that the liver must produce, which it does via the process called gluconeogenesis. Consuming zero carbs puts the body into the metabolic status that drives gluconeogenesis. If we are consuming 120 grams per day of carb, as the subjects in this study apparently were, then we are riding on the edge in terms of driving gluconeogenesis. We probably are making a little sugar to bridge the gap, but probably aren't in the metabolic status most of the day that gives the low-carb diet its real advantage. It's interesting to note that the data from this study show that only about 8 percent of those in the low-carb diet arm were spilling ketones in their urine, which leads me to believe that most were probably not gaining the full metabolic advantage that a low-carb diet offers.
Despite the instruction to increase carbs to 120 grams per day, I believe these subjects had a long-term benefit from the two months of rigid low-carb dieting (20 grams per day) with which they started the study. Why do I believe that? There is a terrific study in Nutrition & Metabolism showing that subjects with diabetes who underwent a strictly supervised low-carb diet for six months, and who lost weight, improved blood sugar control and lipid parameters, were still showing the positive effects of this intervention 44 months later. These impressive findings seem to indicate that there is some sort of rejuvenation that takes place in people after they have spent a period of time on an honest-to-God low-carb diet that carries over for several years. Maybe this is the phenomenon we're seeing in the subjects in this NEJM study. The two months of rigid low-carb carries over for the rest of the study despite the subjects cranking their carbs up to non-low-carb levels.
It's really too bad that the researchers didn't check all the lab parameters and measure weight loss after the two month induction period. And it's too bad they made the silly recommendation to go vegetarian low-carb. And it's too bad they encouraged the subjects in the low-carb arm to increase their carbs to 120 grams per day. But despite all these missteps, the low-carb dieters were still triumphant over the other diets. It just goes to show what a powerful metabolic strategy restricting carbs is."

No comments:

Post a Comment