If you can't figure out why your waistline is not where you'd like it to be, Dr. Ian Smith says it's no wonder thanks to food portions that have ballooned in the past 50 years. "A serving size is what is recommended that you eat. In the old days, by the way, a serving size used to equal the portion we ate," he says. "Now? Forget it! They're almost double sometimes." So how do you know how much of that sandwich you should really be eating at one meal? Dr. Ian is sharing his portion guidelines using familiar objects like a tennis ball or hockey puck to use as a gauge for the proper size of a portion. [Click here for all of his portion guidelines](/portion_guidelines/)! Only Online: What about snacks? Dr. Ian chats backstage and [shares proper portion sizes for some of your favorite snacks, including candy! ](/blogs/2012/09/25/backstage-pass-dr-ians-snack-guide/)