Why do we pick up pounds in the winter even when we're working out?

It seems that no matter how hard we are working out or eating right, many of us tend to gain or maintain weight during the winter and find it's so much easier to lose weight in the warmer months. True, there are more options for activities when its nice and sunny outside than when its cold and dreary, but that's not all there is to it. The reason for this frustrating phenomena may lie in the fact that when it's cold, our bodies burn fewer calories (unless you're freezing - i.e. shivering) than in the heat.

According to Dr. Mirkin, "The hotter it is, the more extra work your heart has to do to prevent you from overheating. More than 70 percent of the energy produced by your muscles during exercise is lost as heat. So the harder you exercise, the hotter your muscles become. In hot weather, not only must your heart pump extra blood to bring oxygen to your muscles, it must also pump hot blood from your heated muscles to your skin where heat can be dissipated.

On the other hand, in cold weather, your heart only has to pump blood to your muscles and very little extra blood to your skin to dissipate heat. Your muscles produce so much heat during exercise that your body does not need to produce more heat to keep you warm. So your heart works harder and you burn more calories in hot weather. This information should not discourage you from exercising when it’s cold, because staying in shape is a year-round proposition."

Another specialist, Dr. Sugar, offers the following perspective; "It is true that different temperatures can affect your metabolism and lead to changes in calories burned. This effect is most dramatic at very cold temperatures when we shiver. Shivering alone can actually burn up to a few hundred calories an hour, but this effect of cold temperatures on metabolism is only significant if you’re actually shivering. It would have to be very cold to shiver while jogging, because so much body heat is generated from your exercising muscles. You will notice that sometimes you sweat less when jogging in the cold because the ambient temperature is keeping you cool.

Very hot environments, like saunas, can slightly increase your body’s baseline rate of calories burned, but it’s not dramatic. As discussed in this LA Times article, researchers have found that sitting in a hot tub burns slightly more calories than sitting on the couch, and we can extrapolate that a sauna would be similar to a hot tub. It is estimated that someone would burn 34 calories sitting in a hot tub for 20 minutes versus burning 23 calories sitting on the couch for the same amount of time. This is not a significant number of calories when you consider that walking for 20 minutes burns 100 calories. The long and short of it is that temperature extremes can affect calories burned, but not dramatically unless you are shivering for long periods of time. More articles can be found here on Dr. Sugar's site Also, along the right hand side are great exercise tips and articles!