Gaining weight with age often occurs so gradually -- a pound-a-year creep is the rule in North America -- you're not quite sure when or why it happened. But 20 years = 20 pounds. Yikes! Don't resign yourself to it.

Here are six things that have the biggest impact on weight gain as you age. Prepare for some surprises.

• Potatoes: If you tend to eat a lot of potato chips, mashed potatoes and fried potatoes, you're more likely to gain weight over the years than someone who favors 100% whole grains and other complex carbs, says new data.
• Red meat: All meat (regular or processed) makes you gain. Fish (as long as it's not fried), fruit and vegetables don't.
• Sugar: Okay, no surprise here. Sugary drinks and desserts (and other highly processed carbs, like white bread) make you bulge out. Naturally sweet fruit doesn't.
• Lifting only light things: Like forks. Weight training builds muscle. Muscle burns more calories 24/7 than soft stuff. Make push-ups and squats an every-other-day habit. No equipment needed.
• Lack of sleep: It affects your waistline. Not least because you eat for energy when you're tired or stay up late. Aim for 6.5 to 8 hours.
• TV: Watching 3 hours a day adds 5 pounds every 20 years. Exercise does the opposite. But you knew that!

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