weight and try to keep it off—they are fighting against the
one-two punch of both lower leptin levels and leptin
resistance. Low leptin increases hunger while decreasing
thyroid activity, sympathetic tone, and energy expenditure
in skeletal muscle, adding up to a major metabolic
slowdown. Anyone who’s undergone massive weight loss
understands this system gone awry: a 250-pound person
who diets down to 200 pounds usually burns about 300 to
400 fewer calories per day than someone who was 200
pounds to start.
On the other hand, recent studies performed by Harvard
obesity researcher David Ludwig suggest that very-low-carb
diets can offset some of this metabolic disadvantage to the
tune of 100 to 300 calories per day—the equivalent of a
daily three-mile run! The great news is that following the
protocol outlined in this book will enable you to achieve this
metabolic “extra credit.”
When we engage in bouts of fasting or very-low-carb
diets, our leptin levels are reduced—but this has the benefit
of increasing the amount of leptin receptors in the
hypothalamus. Thus, by fasting, we can regain leptin
sensitivity, and by incorporating periodic high-carb, low-fat
“refeeds,” we can keep our metabolism revving like a sixties
muscle car (for more on this, see the sidebar on hacking
leptin).
HACKING LEPTIN TO LOOK BETTER NAKED
Once you are fat adapted, periodic high-carb meals can be a