I recently ran into a former patient who had moved away a few years ago. She is a very petite and she had gained about twenty pounds the last time I 
saw her. This time she was very slim. I asked her how she did it. She told me that she had stopped eating protein bars every day which is something that I had suggested years ago.
Why would protein bars make you fat? There are two reasons. First, many protein bars get their protein from soy. Soy can change estrogen metabolism and in higher doses or consumed frequently (as in this patient), can help to raise estrogen levels. Estrogen is a anabolic steroid and tends to make us soft and round like a pregnant women. The second reason has to do with sugar metabolism. Protein bars that don’t have added sweeteners tend to not taste very good so the manufacturers will either sweeten them with sugars or artificial sweeteners. The added calories from the sweeteners of course will be a problem but many people don’t realize that artificial sweeteners can have the same effect. Artificial sweeteners will cause insulin resistance eventually sending all of the carbs that we eat directly to storage (fat cells).
So bottom line, avoid those protein bars unless it is an emergency.
