Air conditioning and fat!

In this weight loss blog I read about air conditioning and fatness.

Air conditioning keeps us in a temperature range in which we do not have to regulate our body heat. Scientists suggest that when people are out of this zone we lose weight. If it's too cold we burn fat to stay warm, and if it's too hot our appetites decrease. Studies show that people are keeping their houses warmer in the winter and cooler in the summer than they did in years past, so these natural influences on weight are negated.

I Saw, than in USA cities very many peoples use air conditioners. My be this is reason why more and more fat peoples we can find in these countries?