||07-24-2009 06:31 AM
Low Carb Diets Cause Obesity, Low Carb Diets Reverse Obesity.
Interesting paper which, if I'm reading it right, suggests that high fat non-ketogenic diets such as Atkins, South Beach etc. (~20% protein) increase adiposity while high fat ketogenic diets (~8% protein) reverse adiposity.
Low-carbohydrate diets cause obesity, low-carbohydrate diets reverse obesity: a metabolic mechanism resolving the paradox.
High-fat diets produce obesity in part because, per calorie, glucose produces greater post-prandial thermogenesis than lipids, an effect probably mediated by glucose-sensing neurons. A very low carbohydrate/high-fat/high-protein Atkins-type diet produces obesity but is marginally ketogenic in mice. In contrast, high-sucrose/low-fat diets, and very low carbohydrate/high-fat/low-protein (anti-epileptic) ketogenic diets reverse diet-induced obesity independent of caloric intake. We propose that a non-ketogenic high-fat diet reduces glucose metabolism and signaling in glucose-sensing neurons, thereby reducing postprandial thermogenesis, and that a ketogenic high-fat diet does not reduce glucose signaling, thereby preventing and/or reversing obesity.
Do low carbohydrate diets promote or reverse obesity?
“A systematic review of low-carbohydrate diets found that the weight loss achieved is associated with the duration of the diet and restriction of energy intake, but not with restriction of carbohydrates.”(Astrup et al., 2004)
“This review covers evidence from carefully controlled laboratory studies, clinical trials, studies in populations at high risk of developing obesity, and epidemiologic studies on the role of sugars, particularly sucrose, in the development of obesity. Although many environmental factors promote a positive energy balance, it is clear that the consumption of a low-carbohydrate, high-fat diet increases the likelihood of weight gain.” (Saris, 2003)
These two statements from recent reviews neatly state the current consensus regarding the effect of dietary composition on obesity. In fact, despite the enormous popularity of low-carbohydrate diets such as the Atkins diet, the South Beach diet and the Zone diet, the professional consensus is that low-carbohydrate diets (which typically implies high-fat diets) are more likely to produce obesity than reverse obesity. Although several studies have reported that low-carbohydrate diets are slightly better than low-fat diets to reduce body weight over a period of about 4-6 months (Brehm et al., 2003; Brehm et al., 2004; Foster et al., 2003), the differences were not significant after a year (Foster et al., 2003; Stern et al., 2004). Similarly, recent “low-glycemic” diets have been promoted as useful for weight loss (Ludwig, 2003). It must be emphasized, however, other studies have failed to support the effectiveness of low-carbohydrate diets (Astrup et al., 2004; Lean & Lara, 2004; Meckling et al., 2004; Truby et al., 2004) or low glycemic diets (Sloth et al., 2004) in long-term maintenance of weight loss. Similarly, although under certain circumstances access to sucrose separately from protein can lead to over-consumption and increased adiposity, this phenomenon appears to occur due to a requirement for sufficient protein and the effect is not observed when protein concentrations are high enough (Kanarek et al., 1987). Certainly many studies have demonstrated the beneficial effects of high-carbohydrate, low fat diets (e.g., the Mediterranean diet: Schroder et al., 2004) in reducing adiposity and other aspects of the metabolic syndrome.