How do you know how much to eat when you sit in front of a plate or bowl of food? Restaurant food usually comes in portions too large for a dieter or someone trying to maintain weight loss.People on diets are told to weigh and measure their food before serving themselves, so they know how much they are eating. Butafter a while, dieters stop weighing and measuring—assuming they had done so—and tell themselves that they can judge how much should be eaten by “eyeballing” the amount of food on the plate. And they believe they know how much to leave behind if the portion looks too large.But can this really be done? What would happen if, despite how much you eat, the amount of food on the plate stayed the same? Would you stop eating? And when?This was the basis of an experiment published in Obesity Research in January 2005. The team of researchers devised a soup bowl connected to a hidden tube that was, in turn, connected to a vat of soup. They asked volunteers to eat the soup, which was tomato. As the soup was consumed, the hidden tube poured more soup into the bowl. The level of the soup in the bowl did drop enough so the eaters did not suspect anything. But the bowl never emptied. The volunteers were allowed to eat only for 20 minutes; otherwise, if they were allowed to eat for a long time, they might have suspected something when they could never see the bottom of the bowl.Other volunteers were given a normal bowl and if they finished all the soup, they were offered more.The volunteers eating out of the “endless soup bowl’” ate 73% more soup than the volunteers who ate from the normal bowl. Yet the endless bowl volunteers did not report themselves as being any fuller or stuffed than the people eating from the non-tampered bowls. In fact, they may have continued eating if they were given more time to do so.Wansink, Painter and North, the scientists who carried out the study, discussed the implications of their findings for weight control. They wrote that if we rely on our eyes to tell us when to stop eating, rather than how full we feel, we are going to find ourselves overeating a good deal of time. People who belonged to the clean plate club as children know this already and try to prevent themselves from consuming too much by making sure the amount of food on their plate is appropriate.“I insist on being served a small piece of cake or pie,” a friend told me. “I know I could eat a really large piece, but I have trained myself to eat only what is on my plate and if it is a small portion, I won’t ask for more.”Fortunately, people who describe themselves as on a “see food” diet (they see food and eat it) can use some simple tricks to prevent themselves from falling into the trap of the “bottomless-soup” eaters.Be aware of how full you are feeling as you eat. Fast eaters are out of luck with this suggestion because they can consume very large portions in a very small amount of time and don’t stop to judge how full they are until they stop eating. If you are one of these people, divide your food into two portions, eat one and wait five minutes before eating the rest. When you start eating again, take a few seconds to ask yourself if you are as hungry as when you started eating. You may find yourself eating less than you had planned.Obviously this did not work for the soup eaters but as the researchers explained, it may be possible to consume more of a liquid meal; i.e., soup, without feeling full.Use small plates. This sounds so simple but it really works. Think of how rice is served in a Chinese restaurant. It comes in a small bowl heaped into a dome and looks like a large portion. But if the rice were put into a large pasta bowl, the portion size would look smaller. It seems irrational but we like to think we are eating enough, even if we know the portion size isn’t large, and small plates help fool us in this way. This also works if you are at a buffet. Salad-size plates limit the amount of food you can take. In fact, smaller size plates are becoming more common at catered events, perhaps to limit the amount of food customers are taking. Even though you can go back for more helpings you are aware of doing so and this helps control the amount of food you are eating.Stay away from restaurants that boast of large portions, including fast-food chains.It might never occur to you to eat a four-hamburger patty, cheese and bacon-filled bun until one is put in front of you. But, like the soup eaters, if it is there, you may find yourself eating it until nothing is left but the wrapper. If you know ahead of time that the portions are too large for your caloric quota, plan on sharing, taking the extra home, or ordering an appetizer rather than entrée.Don’t eat out of large containers of ice cream, snacks, cookie packages, and bags of candy.This is a prescription for caloric disaster, since you may continue eating as long as you see the food.Let your stomach be your eyes. As you begin to feel full, don’t let the presence of uneaten food motivate you to continue eating. You will see the results on the scale.