04/18/2016 03:32 EDT | Updated 04/19/2017 05:12 EDT

The Hidden Ingredient That Could Be Making You Fat

Markus Guhl via Getty Images
A woman's stomach bulging over the waistband of her jeans.

There's a controversial, hidden "flavour-enhancing" product in many processed foods that may cause you to pack on the pounds.

It's earned a dubious reputation over the past several decades. So it now goes by up to several dozen different aliases. They include such innocent-sounding ones as hydrolyzed vegetable protein, natural meat tenderizer, malt extract, hydrolyzed protein, autolyzed yeast, glutamic acid, yeast extract, and even natural flavouring.

However, it's best known as monosodium glutamate (MSG), and it's been linked to weight gain by numerous medical studies. They include a five-year study that examined the eating habits of over 10,000 people in China.

Led by Dr. Ka He, an associate professor of nutrition and epidemiology at the University of North Carolina at Chapel Hill, its findings created quite a stir when the study was published in 2011.

Dr. He's international research team discovered that people who consume plenty of MSG are far more likely than both light consumers and non-users to be overweight.

Dr. He also found that people who consume MSG have higher levels of the appetite-regulating hormone, leptin. In other medical studies, it's been clearly shown that too much leptin can cause people to keep eating when they should feel full.

And even though Dr. He's study only involved Chinese citizens, there's no reason to believe that MSG would affect other ethnicities differently, the scientist says.

Some animal studies also indicate that MSG may promote weight gain. For instance, scientists have discovered that they can induce obesity in newborn laboratory rats by injecting them with MSG.

If you visit the National Library of Medicine online at, and type in the words "MSG Obese," dozens of medical studies are listed on this subject.

Once again, MSG is found in many industrialized food products. They include luncheon meats, canned meats, hot dogs, and all manner of processed convenience foods -- such as salty flavoured snacks. It's also commonly used by most fast food outlets, and in large quantities.

Critics of MSG say this is because it causes people to eat more than they normally would if it wasn't present. They also claim that it's addictive.

If both -- or either -- of these claims are true, then the food manufacturing industry can depend upon MSG to keep driving up food sales for many years to come.

Meanwhile, the U.S. Food and Drug Administration and its Canadian counterpart, Health Canada, have set no limits on how much MSG can be added to foods. They claim that it's safe to eat in any amount.

However, Health Canada admits that it may induce "an allergic-type reaction or hypersensitivity" in some people, involving some of the following symptoms: "a burning sensation, facial pressure, headache, nausea, and chest pains."

So if you're buying packaged supermarket foods, try to remember to read each product's list of ingredients, especially canned goods, to ensure that you're not unwittingly consuming MSG. And once again, beware of fast foods, especially fried chicken, burgers and fries -- all of which are typically loaded with MSG.

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