When it comes to portion control, the eyes have it. In fact, according to several recent studies, what your eyes see on the plate determines to a significant extent how much you eat.

For example, if there are 20 cashews in a bowl, you might take six or seven (52 calories). However, if there are 50 cashews in a bowl, you’re more likely to take a handful of 15 (130 calories). In both cases your eyes will tell your stomach and mind that you’ve had a moderate portion – but the “moderate portion” from the larger bowl has 80 more calories.

This can make a big difference to weight control, as one study involving grad students at a Super Bowl party shows. When the students served themselves Chex Mix from two different-sized serving bowls, those who ate from the 4-liter bowl consumed 42 percent more of the Chex Mix than those who ate from the 2-liter bowl.

When asked to take a “normal” serving size of Chex Mix from two different-sized bowls, participants in a related study took 50 percent more from the larger bowl.

Portion control tip: Both of these studies show that the bigger the serving bowl, the more you tend to eat because you think it’s a “normal” amount. To overcome this portion distortion, try serving your food on smaller plates or weighing your food so you know exactly how much you’re eating. Don’t rely on your stomach to tell if you’re full!

Although food companies are starting to downsize product packaging, large package sizes are still a major barrier when it comes to portion control.

Studies show that larger package sizes make people use more. Brian Wansink and his team at the Food and Brand Lab at the University of Illinois have conducted over 50 experiments involving everything from M&Ms to spaghetti to popcorn to laundry detergent, and found that larger packages can cause people to consume up to 48 percent more.

So while it might seem like you’re getting a good deal when you buy a large bag of pretzels for only 40 cents more than the regular size – you’re not saving anything in terms of calories. In fact, you’ll "spend" more. You also don’t save much when it comes to cost. Research has found that you simply use more or waste more. From this standpoint, a larger package can often be more costly.

Portion control tip: Aside from the obvious advice to buy smaller packages, try purchasing the bulk-size product and then splitting it up into reasonable portion sizes in separate containers when you get home. That way you really do get a good deal without spending unnecessary calories.