The following are the uncontrollable factors that affect our metabolism:

• Age -- Metabolism naturally slows about 5% per decade after age 40. That's mainly because as we get older, we tend to lose muscle and increase body fat. Lean muscle mass is more metabolically active than fat tissue. Thus, when you lose muscle, your metabolism slows. 

• Gender -- Men generally have faster metabolisms than women because they're larger and naturally have less body fat. It's been estimated that men have 10 to 15% higher basal metabolic rates than women.

• Hypothyroidism -- An under active thyroid will slow down metabolism and ultimately lead to weight gain. Good news: A simple blood test can validate this condition and with proper medication, your metabolism will soon be back to normal.

• Genetics -- Some people are lucky enough to be born with speedy metabolisms, while others are not.
  
  

Supplements

So what about the over-the-counter supplements?

I do not recommend them. The ingredients that are effective tend to boost metabolism only slightly and can often be risky. High dose stimulants can make you jittery, increasing your heart rate and blood pressure.

The bottom line: The safest and most effective way to boost your metabolism is to eat an appropriate amount of food every 4 to 5 hours, incorporate lean protein with each meal, and exercise regularly!

In my next entry, I promise to discuss several positive things you can do to boost your metabolic rate. Stay tuned!