I exercise almost everyday, doing a variety of activities ranging from running to yoga. But over the years, I find it so hard to lose weight (as well as maintain my ideal weight) and so easy to gain weight!
True story: when I was younger, around age 16-18, I barely exercised at all. I don't do sports. I'm the typical nerd sitting at home studying. I sleep a lot during the summers. And the thing is, I don't weigh a lot! Despite my sedentary life (and normal appetite, not that I'm starving or anything), my BMI was very low. I was at my ideal weight.
Fast forward to many years later. I exercise almost everyday, but still 5 lbs overweight. I used to run 2 miles a week but still see no results in weight loss. It's like no matter how much I exericse, I am still several lbs above my ideal weight (compared to ages 16-18 when I am at my ideal weight). I remember successfully reaching my ideal weight approximately 1 year ago, when I dieted at my peak. But I have since gained back the weight.
I have several theories for this. 1) BMR decreases as we age. The amount of calories we burn at rest is higher in younger people than older people. This explains why I burn less calories as I age. 2) muscle loss. We start losing muscle after the age of 20. We lose around 5-6 lbs of muscle per decade. Muscles are important for dieting because they help us burn calories.
Go figure. No wonder it's so hard to lose weight as we age. I recommend people lose weight earlier rather than wait until, say age 40 or 50 to do so.