Fat is not fattening. Weird, but true.

Most people worry that eating fat will make them fat. And it's no wonder-- we have been told this for decades. And, we know that fat has more calories per gram than carbohydrates or protein. So the assumption is that fat makes you fat. Why, then, as we have cut back on fat, especially saturated fat, have obesity rates tripled?

Our bodies are incredibly complex. Hormones play a huge part in regulating everything, and body weight is no different. It turns out that if you want to burn your own body fat for energy (which is essential if you want to lose weight), you must have low insulin levels. Insulin, you see, tells fat cells to pull fatty acids out of the blood and to keep fat in the fat cells. Whenever you eat carbohydrates, you body floods your bloodstream with insulin. So eating more carbohydrates means less time in fat burning mode. Which means more fat accumulation in the fat cells. Which means hunger and weight gain. Eating more fat and fewer carbohydrates means easier fat burning, less hunger, and a better shot at losing weight.

Leptin is another hormone important for feeling satiated. But insulin dominates, and interferes with leptin's ability to make you feel full and satisfied. So, when insulin is present, due to excess consumption of refined carbohydrates, it turns off leptin's signals, leaving you unsatisfied and on the road to weight gain.

Repeat after me:  Eating refined carbs makes you fat.  Eating good fats makes you thin.

More from the experts:

Dr. Andreas Eenfeldt on how Low Carb High Fat works to reduce weight.

Clip from Fathead, the movie, entitled 'Why You Got Fat.'

Dr. Robert Lustig, a pediatric endocrinologist from UCSF, explains the role hormones insulin and leptin play in weight gain and obesity in this ~8 minute video.

Infographic from Gary Taubes and Massive Health about why fat doesn't make you fat.

Infographic from Massive Health: 'What makes you fatter -- bacon and eggs or a bagel with low-fat cream cheese?'