Many people try avoiding MSG (monosodium glutamate) even though the food industry calls it the "safe" flavor enhancer. Some people have read about the negative associations with it and others get a headache or upset stomach after consuming it. So if you weren't convinced to avoid MSG, here is one more reason: It might be causing you to gain fat.
Researchers have been using MSG to "fatten up" lab rats during experiments, but they had never looked to see if it had the same effect on people. Why wouldn't the FDA, require this kind of test, before saying it is a safe food additive, is what I would like to know. So, researchers in at the University of North Carolina and research counterparts in China, decided they would find out if MSG made humans fat, like their lab rat counterparts.

The study compared MSG consumption of more than 750 Chinese men and women. During home food preparation in China they use a lot of MSG, we most often find it in restaurants and packaged foods here in the US.

Coincidentally (or not), the subjects who consumed the most MSG were more than 300% more likely to be overweight when compared to those not using MSG, even after adjustments for other variables that are often associated with weight gain (ie: physical activity, caloric consumption).

So, why does MSG causes weight gain? One theory is based on the lab observation of rats that were given MSG. They tend to eat more, than when not consuming MSG. This indicates that MSG somehow affects appetite, and when our brain signals satiety.  

The other main factor is how MSG disrupts blood sugar levels. Several Studies have found that when you give normal rats excessive amounts of MSG, you can cause severe insulin resistance. When the rats were given MSG they stored more glucose as fat than their normal counterparts not being fed MSG. 

Even though we aren't sure of why MSG causes weight gain, it appears that once again, it may not be your fault you're getting fat, take back control of your life by avoiding MSG when ever possible.

You are probably not using much MSG when you are cooking at home, but you are very likely to be getting a lot of MSG when you dine out. Also, make sure you are reading labels when you shop. Watch out for soups and salad dressings (especially Asian-style). Many flavor-coated foods - like nacho and barbeque flavored chips also contain high levels of MSG. 

So, to avoid unnecessary fat gain, try to prepare food at home as often as possible, and try to stick to whole natural foods without bags, cans, or labels. Eating in is a great way to build social support, build relationships with family, and teach good getting habits to our children.