As someone who has lost a modest amount of weight by obsessively counting calories, I have an insight into certain things that most people might not notice. Several of these insights are with regard to dining at restaurants, the most important being portion size.
Everywhere I eat, it seems that the caloric values of the food being served per person is much, much too high. An example is a burger with fries; regardless of which place you are eating, if it is a chain restaurant like Chilis, then you should expect a meal that consists of about 1300 calories, and that is without considering any additional condiments you might add after (like ketchup or ranch.) On my diet, both past and present, I have set a caloric intake value of 1500 per day. Thus, if I want to eat out, I have to know ahead of time and eat only minuscule amounts the remainder of the day, or the other option I have recently adopted: eat only half and take the rest home.
Even if not on a diet, I'd be amazed if it could be shown that anyone actually needs to consume 1300 calories at one meal. Mathematically, most men probably need no more than 2500 per day. If you eat 1300 in one meal, you are left with only 1200 for the rest of the day. So, while it is doable, the meal would necessarily be huge (more than twice as much) as each of the other meals for the day (assuming three meals). Eating out twice in one day (which happens frequently to those who travel for business) means eating more calories than one needs. And, most people like to snack at various points along the day, which becomes trickier.
A reasonable strategy is the one I listed above: eat only half the meal. A good rule of thumb is: if you are looking at your plate and think it looks like enough food, it is likely more than you need. If it looks like it isn't enough, then you are likely eating the right amount. Half a meal always looks too little, but it is plenty big enough. Take the other half home and eat it for dinner or lunch the next day. Or, if you really don't care for leftovers, either split with someone or just throw it away. Remember, it isn't a waste if you really don't need the food. I have had some limited success with convincing the guys I go to lunch with that we might consider ordering one thing and splitting it between two. If enough people did this, I am certain restaurants would change their portion sizes accordingly. Until that time, I am content to get a half-off deal on all my lunches.
I wonder why portion size is so ridiculously large in the US? I suspect it has to do with the concept of getting your money's worth: the more you get the better the deal. It also likely has to do with the cost of food to the restaurant: food is cheap, but the markup on it for being served is significant, and even more of a markup can be included if a larger portion is served. It might also have to do with the balance of quantity and quality: when I eat at the nicer restaurants, the portion size always seems much more reasonable.
As I briefly insinuated above, I have taken up my caloric restriction again; I had stopped keeping track and found it was very easy to return to my old ways of eating. A couple of months ago, I decided I needed to re-do my diet before it got way out of control. At 200 lbs, I wasn't even close to approaching my original pre-diet starting weight of 230 lbs, and I have already dropped back to a more reasonable 186 lbs. My intent is to get my weight to 180 lbs and then schedule my yearly free "healthy checkup" with my doctor. At that time, I'll discuss what a reasonable weight for me is. According to BMI, I'd need to drop to about 170 lbs to be at the top of the "normal" range, but BMI isn't a very accurate way to determine if you are at your ideal weight.