Liz Neporent is a diet and fitness expert and author of 12 fitness bestsellers. She regularly appears on national TV programs and is the president of Wellness 360, a New-York based wellness provider.

Recently on this blog, I've talked about how you can't always trust food labels. This week, I want to talk about food packaging -- something else you probably shouldn't trust. Food packaging and portions have undergone the same transformation as our national waistline -- they've gradually gotten bigger and bigger and bigger. Foods like cookies, muffins, candy bars, steaks, sodas and countless other foods started blimping out during the 1970s, dramatically inflating in the 1980s, and have continued to swell, to the point where some food products are now Godzilla-sized versions of their original selves.

Food portions weren't always so massive. Back in the 1950s, McDonald's offered just one size of French fries; that size, containing 210 calories, is now the smallest on the menu -- the largest contains a belt-busting 610 calories. The 7-Eleven Double Gulp, a 64-ounce soda (nearly 800 calories) is 10 times the size of a Coca-Cola when it was first introduced in 1886. In fact, beverage sizes have ballooned so much over the past generations, auto manufacturers have had to install larger cup holders to accommodate them.

Studies show that muffin tins, restaurant dinner plates and pizza pans are growing too. Even cookbooks suggest larger portion sizes than in the past: In a 1960s version of "The Joy of Cooking," a brownie recipe was considered to serve 30 but now the exact same recipe serves only 16 brownies!

Much of this portion size porking up appears to have happened without consumers noticing. But we've certainly noticed how much our waistlines have expanded. Not surprisingly, our regular consumption of super-sized fries (though no longer offered in many fast food joints) has led to a nation of super-sized thighs. With 65 percent of Americans now considered either overweight or obese and nearly half a century of failed diet and exercise plans, it's more important than ever to pay attention to portion size. It's one thing research overwhelmingly points to as a successful, proven weight loss method. For example, the highly respected National Weight Control Registry, an on-going research study that tracks more than 6,000 people who have lost weight and successfully kept it off, points to portion control as their number one weight management strategy. (As regular readers know, I reference the NWCR in this column on a frequent basis because I believe it is one of the few reliable sources about safe, permanent weight loss.)

If you only do one thing in the name of weight loss, practice portion control. Invest in a set of measuring cups and a kitchen scale and measure everything you stuff in your mouth for a week. You can get a list of recommended portion sizes by clicking on mealsmatter.org. Also, whenever you eat out, try immediately dividing your plate in half and asking for a doggie bag right away. A typical restaurant serving of pasta, for example, is 10 times a recommended single portion size! Your first clue should be if your food is spilling over the sides of your plate. Your waist line will thank you for being aware -- and you will be amazed at what a portion size really is -- and isn't.

Do you practice portion control? Has it helped you lose weight? Ever eat anything bigger than your head and live to regret it? Feedback please ...