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By Diane Henderiks

Do you find yourself thinking,"I used to be able to eat anything and everything and not gain a pound"? If so, what happened?

First and foremost is that our nutrient requirements increase or remain the same as we get older while the number of calories we need goes down. So what do we need to do? Eat nutrient-dense foods, watch your portions and exercise more.

Also, for many people changes in "metabolism" can make them more susceptible to weight gain. But what actually is "metabolism"? The word is tossed around so much but how many people actually know what it means? I found numerous definitions for "metabolism" while researching for this article and here is the simplest one:

metabolism: the chemical and physiological processes by which the body builds and maintains itself and by which it breaks down food and nutrients to produce energy.

Layman's terms - metabolism is how YOUR body uses energy from food to build and repair tissues and organs and how efficiently it does this is a key to weight management. A great way to succeed in losing weight and keeping it off is to increase your metabolism and a great way to do this is to add strength training exercises to your physical activity routine. Muscle tissue is much more "metabolically active" than fat. This means that the more muscle you have on your body, the more calories you will burn regardless of your age, physical activity level, gender, etc. An added bonus is that muscle tissue continues to burn calories at rest.

This does not mean dreading the thought of spending endless hours at the gym. There are simple exercises that you can do to increase muscle mass which will decrease fat mass. If you like to walk and it is usually on the boardwalk or side streets, find a course that has some hills and you will be adding resistance to your walking routine. If you walk on the treadmill or use the elliptical machine, crank up the resistance for a fun, cross training workout. Get yourself some hand weights and have someone to show you how to use them.

Diane's Top 5 "Prime Time" Health Tips

1. Combine cardiovascular and resistance activity to your daily exercise regimen.

2. Choose foods as close to their natural state as possible - whole grains, fruits, veggies, nuts, and seeds.

3. Reduce sodium, sugar, unhealthy fats, packaged and processed foods in your diet.

4. Drink lots of water, avoid sugared and artificially sweetened beverages and limit alcohol intake.

5. Get enough sleep for increased energy level, clearer thinking and stress reduction

We grow smarter and wiser with age so let's use these years of intelligence building to do what is necessary to keep us healthy. Maybe we feel a little entitled to be lazier and make unhealthier food choices because we think we've earned it but if you really think about it, the "prime time" of life is when you want the MOST energy to enjoy the stress-free mornings and increased free time. We obviously cannot stop aging, but we do have control over our lifestyle choices, food choices and physical activity. Use it, move it or lose it.

Diane Henderiks is a registered dietitian, the founder of Dianehenderiks.com and a "Good Morning America" health contributor.