From overeating comfort foods to soft lighting, get the scoop on the weird factors that interfere with losing weight

Choose your meal-mates wisely. If you eat with an overweight friend, you're more likely to overindulge, shows a new study in the journal Appetite. That's the case whether your plus-sized pal eats healthy stuff or junk food too, the study shows. Just as playing sports with uncoordinated friends makes you feel like a super-skilled athlete, eating around overweight people makes you feel slim. And that altered self-perception lowers your motivation to eat right, the study authors say. Here, seven more things that affect your weight loss goals in unexpected ways. (If you find yourself overeating, get back on the healthy track with Your Post Pig-Our Plan!)

A Good Mood



Movies love to point out the old eating-ice-cream-after-a-break-up cliché. And while it's true that you reach for comfort foods when you're sad, being in a happy mood also cranks up your appetite, shows a U.K. study. Happiness not only distracts you from counting calories, it also makes you worry less about sticking with your diet goals, the authors say. (But if you can't resist indulging in a slice of chocolate cake, try making these 11 Crazy Delicious Desserts with Hidden Healthy Foods.)

Chilly Temps



The colder the ambient temperature, the more you eat. Your body uses food (and body fat) to keep you insulated and warm. So you tend to both eat more and retain more fat in cold climates than in hot ones, shows a study from Yale University.

Dim Lighting



Dim or soft lighting increases consumption in two ways, according to research from Cornell University. First of all, low lighting makes your environment more comfortable, which causes you to linger over a meal. Also, if you're dining with other people, low lighting makes you less self-conscious about both your body and the dessert you're chowing on, the researchers suggest.

Speedy Tunes



The faster the music's playing at a restaurant, the faster you'll eat, according to research from Scotland. That could be a good or bad thing depending on how much you're served. Your eating speed can outpace your brain and belly's ability to detect whether you're full. So if you have a lot of big plates in front of you, speed eating may lead to overconsumption, the study shows.

Inviting the Whole Group



The more friends you dine with, the more you eat. According to the study from Georgia State University, every buddy you add to your dinner party ups your consumption by about 11 percent. Friends tend to keep eating as long as someone else is still going at it. So the more pals you're with, the longer the meal will last.

Long Reads



Do you sit down to eat with a magazine? The longer the mag, the more you'll eat. People who eat and read tend not to stop munching until they've flipped through the whole issue, shows a study from Finland.

Ordering a Large



The bigger the package, the more you eat. For example, if you're offered a jumbo chocolate bar or soda, you'll consume 15 percent more than if the bar or bottle were small, shows research from the Journal of Marketing. (What a bummer! Luckily, there's an app that can tell you What 200 Calories Really Looks Like.)