From the age of 40 when our hormones begin to change and prepare us for the ageing process, our metabolism needs to be kept high and that won't happen unless we control it. Yes, men do naturally have a higher metabolic rate than a woman but a woman can elevate her metabolic rate to burn fat for the rest of her life. Don't use age as an excuse to slow down. The only time the metabolism may be unable to fire up through moving and building muscle, is if one has an under-active thyroid or Cushings Syndrome.