With two out of three Americans overweight today, it’s getting harder to believe that all this extra fat is a simple problem of self-indulgence or poor personal discipline.

In fact, researchers and clinicians from various sciences say unequivocally that it’s not. Certainly adults are responsible for what they put in their mouths. But when so many are affected, from all across the American demographic, we have to also look what’s going on in our culture at large.

And one thing that’s going on is that there’s a lot more going out. In 1978, just 18 percent of the calories Americans consumed were eaten away from home. But by 2003, that was up to half.

Why should that even matter? A calorie is a calorie is a calorie, right?

At the bottom line, yes. The trouble is that when we eat out, we simply have much less control over what ends up on our plates, and from there, on our bottom line. That shows up in a variety of ways.

Nutritional research indicates that for almost any given dish that you might choose to prepare at home, when it’s compared to a restaurant dish of the same name, it’s often not the same thing at all. So even trying to consciously select what looks like the healthiest choice on the menu might not do you much good.

Restaurants tend to use more oils and fats, more sugar, and more salt in their food preparations. The reason is simple: if the food is yummy, you’ll come back! But that tends to add up to a lot of extra calories you weren’t counting on.

And speaking of extras, how about all those extra nibbles: the plates of appetizers, the baskets of warm bread with pots of cool butter, the bonus beverage specials? Most families simply don’t have all those edible accouterments with regular home meals.

But at a restaurant, your drinks are brought before you even order. You often get bread or rolls to eat during your wait, and appetizers and desserts are helpfully suggested by your server.

Yet those extras can have even more calories than your meals! An order of buffalo wings with blue cheese dressing? That’s a tidy 1,010 calories before dinner. For a fried onion blossom with dip, figure around 2,000. Even a basket of garlic bread is about 800 calories. How many people are sharing those calories at your table?

Then you get to the main attraction, and the major problem with dining out–portion size! Restaurant meals are often three to four times larger than a normal serving size.

Even plates, glassware and utensils have grown. Very often, the dinner plate you get in a restaurant would qualify as a platter in any home kitchen, but then, they have to be bigger to accommodate those super servings!

It wouldn’t be such an issue if we were better at walking away. An old adage about fitness says that the most important exercise to do is “pushbacks,” as in, when you’ve had enough, push back and get up from the table.

But research shows that Americans in general tend to be “completers,” and many of us were raised to feel a sense of guilt if we left food on our plates. Add that programming to a giant dish of pasta, and suddenly, you’re stuffed!

The truth is, no matter how we’re raised, or whether we’re slim or fat, if more is put in front of us we’ll eat more, period. And usually, we’re not even particularly aware of it. This has been proven out by study after study, in both the United States and abroad.

And that’s not all. The research also shows that as we become accustomed to those mega-sized meals we’re presented in restaurants, we tend to prepare bigger portions at home, as well. We may not use all the extra oil, salt and sugar that restaurants do, but we’re certainly having more of our main ingredients, and we’re eating big and hearty.

The other thing that restaurants have over the home meal is variety. Even the most accommodating home cook typically won’t make a different special meal for each member of the family. Again, the nutritional research shows that the more different things you can have, the more you’ll eat overall.

United States Department of Agriculture studies showed that when offered three varieties of a given food item–say, sandwiches or cookies–people would eat more than if they were offered three items of the same variety. That’s part of why those all-you-can-eat buffets are such a caloric catastrophe. Who ever has just a little?

Given the demands of today’s busy lifestyles, dining out nowadays is not only a pleasure, but a time-saving survival tool. Restaurants may eventually be required to provide nutritional facts for their meals, but even without hard numbers, awareness of the pitfalls can go a long way toward helping us control those calorie counts.

We just need to think about what we’re up against when someone else is serving, so that when we’re eating out, we’re not taking so much in.