Weight Gain: Why Does It Happen?

Unwanted weight gain is a global problem. The World Health Organization estimated in 2005 that 400 million adults were obese (Body Mass Index > 30); and 1.6 billion were overweight (Body Mass Index > 25). If current trends continue, the WHO estimates that by 2015, 700 million adults will be obese, and 2.3 billion will be overweight.

Why are so many people gaining so much extra weight?

The Caloric Balance Hypothesis Tells Us:


OvereatingInactivityObesity

The Lipophilia Hypothesis Tells Us:


Diets High in CarbohydratesElevated Insulin LevelsObesity

Most people are familiar with the mainstream theory - what we are calling the Caloric Balance Hypothesis. This is the obvious-sounding idea that overeating calories and/or not burning off enough calories makes us fat.

There is an alternative theory, however. The Lipophilia Hypothesis tells us that hormonal action on the fat tissue causes obesity. When we gain fat in our fat tissue, this causes us to overeat and/or to become inactive. Calories don’t "count," after all. What "counts" is the size and disposition of the fat tissue itself.

So what does the evidence tell us about which theory is right? (Click on links below to find out.)

1. Overeating calories does not make us fat.

2. Sedentary behavior does not make us fat.

3. Obesity may associate with a positive caloric balance, but that does not mean that excess calories necessarily cause obesity.

4. Increased levels of the hormone insulin does cause weight gain, independent of changes to diet or exercise.