Increased intestinal permeability may lead directly to increased hunger, and a higher bodyfat setpoint.

In yesterday's Part 3 in the Body Fat Setpoint series, Stephan lays out his theory about how leptin resistance occurs, and how that affect out body fat setpoint. It's a little bit dense, so I decided to summarize it to the best of my ability here, as well as incorporate some of my own thoughts:

• Increased intestinal permeability allows inflammatory substances, such as LPS* (lipopolysaccharide), to cross the gut barrier into our body.
• The inflammatory substances irritate many tissues, including the hypothalamus. The hypothalamus is the main site of leptin's action. Leptin is a hormone which causes increases in energy expenditure and reduced appetite.
• Irritation of the hypothalamus causes it to become leptin resistant, which means that the energy-increasing/appetite-suppressing effects of leptin are blocked. We get more tired and hungry.
• There are many things that are known to increase gut permeability: gluten, lectins from grains, legumes, and nightshades(tomato/potato/eggplant), certain substances in dairy, alcohol, capsaicin(hot peppers), saponins, abnormal gut flora, omega 3:6 imbalance, and much more.
• A paleo diet eliminates nearly all of these offending substances, which helps improve gut barrier integrity.

*Lipopolysaccharide is produced by gram-negative bacteria, and is one of the main component that the immune system uses to recognize these pathogens. LPS causes a strong activation of the immune system.