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Old 12-19-2006, 08:59 AM   #1
Steve Shafley
Senior Member
Join Date: Oct 2006
Posts: 1,273
Default Insulin Sensitivity vs Insulin Resistance

Kelly Baggett (see the Fitness and GPP forum) had this interesting bit to say about insulin sensitivity vs resistance. This was in the comments of the latest Poliquin article on T-mag.

Actually people get confused because they think being extremely insulin sensitive is a good thing. What most think of as carb tolerance is actually a form of carb intolerance. Hypoglycemia is an example of extreme insulin sensitivitity (hypersensitivity actually). Someone who can eat a big ass carb meal (like pancakes) and not get a blood sugar crash is actually probably resistant to insulin....their blood sugar goes up and stays elevated. An extreme example of that is diabetes.

From that perspective, african americans naturally tend to be at one end (the more resistant end) and american indians at the other end (the hypersensitive end). Sensitivity predicts weight gain. Someone who is insulin resistant is in a state that their body is basically rebelling against further nutrient storage..actually giving them an advantage for burning fat.
The same things that make a person achieve leanness and muscularity with hardly any effort can also make them succeptible to obesity. Basically they develop reistance to insulin and leptin at a lower level of fatness. Once the resistance has set in, the metabolic regulation becomes such that the brain thinks it's starving even though it's well-fed.

A person can become fat due to either underactivity of various hormones and neurotransmitters in the brain or overactivity. Insulin and leptin resistance are examples of the latter. Hypoglycemia is an example of the former.

People with higher natural levels of fast twitch muscle fiber have a greater risk of IR and obesity later in life.....but if you train them and keep them somewhat lean they are the true freaks...lean, muscular, strong.

To understand why a certain level of IR can be desirable for an athlete think of what happens when you bring a person with a big beer gut into the gym and start training them for the first time. They build muscle and burn fat like there's no tomorrow. But what happens when that same person sits on their butt? They develop even more obesity and health problems.
Metabolic predictors of weight gain.Ravussin E, Gautier JF.
Clinical Diabetes and Nutrition Section, National Institute of Health, NIDDK, Phoenix, Arizona 85016, USA.

Human obesity is the result of both environmental and genetic factors. In this manuscript, we briefly review the metabolic factors predicting body weight gain in Pima Indians, a population prone to obesity. The metabolic predictors of weight gain are: 1) a low metabolic rate, 2) low levels of physical activity, 3) low rates of fat oxidation, 4) insulin sensitivity, 5) low sympathetic nervous system activity, and 6) low plasma leptin concentrations. In contrast, obesity is associated with high metabolic rate, high fat oxidation, low insulin sensitivity and high plasma leptin concentration. This observation emphasizes the need to conduct prospective studies to obtain a better understanding of the etiology of obesity. In addition, genetic studies will help to identify new pathways involved in the pathophysiology of obesity.
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