It’s the holidays and everyone seems to be on a diet. So I thought it would be a good idea to answer a question I’ve been getting asked recently on a pretty regular basis. The question is: Can you lose weight by eating foods that take more calories to digest, than they contain? These foods are popularly called “negative calorie foods”, and there’s been some talk recently about negative calorie foods and how they help you lose weight. Here’s the run down on negative calorie foods. The process of digesting food burns calories, and a few foods such as grapefruit and celery contain fewer calories than it takes to digest them, so when you eat these foods, you actually burn more calories than you take in, thus the term negative calorie foods. Now, theoretically the more negative calorie foods you eat, the more weight you’ll lose. Sounds great right? Now, the only other things you need are a job that pays you more the less you work, and a bank account that gets bigger the more I spend. Unfortunately, it doesn’t work that way, and here’s why. When dietitians, like myself estimate how many calories you need to eat, we’re already taking into consideration how many calories you burn by just functioning as a human being on a daily basis. The “negative calories diet scheme” is essentially subtracting those calories twice. That’s just going to put you into a bigger calorie deficit than you need and will more than likely lead to you not seeing much progress in the long run at all. Now, grapefruit and celery are great options for weight loss foods, but only because they are lower calorie and more nutrient dense than you afternoon bag of chips or empty calorie snack. Replacing high calorie foods with low calorie foods CAN help you loose weight because it reduces your overall calorie intake, and of course coupled with exercising, which burns calories, will be your best bet for loosing and keeping the pounds off. Those lists of negative calorie foods on the internet, are simply a list of low-calorie foods, and if you’re dieting, these foods are definitely your friends. So in response to the negative calorie dieting, I’m afraid it’s just too good to be true.
While you’re looking up negative calorie foods in the internet, you’ll probably run into the myth of drinking ice cold water and how it speeds up your metabolism. The idea behind this is that your body has to burn calories to re-warm itself up to normal body temperature because of the cold water you just drank. But lets do the math. By definition a calorie is the amount of energy it takes to raise the temperature of 1 gram of water by 1 degree Celsius. So, a 16-ounce glass of water is about 470 grams. The temperature of ice water is 0 degrees Celsius and body temperature is about 37 degrees Celsius. So lets do the math, 37 times 470 equals 17,390 calories. That is WAY more calories than you can burn in half an hour on the treadmill. So there is a small wrinkle in this logic of thinking. When we talk about calories in regards to food and nutrition, we’re actually talking about kilocalories, which you might see abbreviated as kcals. A kilocalorie contains 1,000 calories. Surprisingly, 1 stalk of celery contains 6,000 calories, but to save the effort of writing all of those zeros, the nutrition is simply written as 6 kcals. And now, in popular use, kcals have simply been referred to as calories, but with a capital C. As it turns out, drinking a glass of ice water actually only burns 17 kilocalories, and to loose 1 pound, you would have to drink 205 glasses of ice water.
We’re almost out of time and I don’t want to leave you with deflated dietary goals, so here’s a quick tip. Instead of following diet schemes and drinking ice water every minute of the day, find ways to incorporate exercise throughout your day. For example: Did Netflix just ask you if you’re still watching a series? I know, so rude right? Happens to me all the time. But, when that happens try getting up and doing some kind of quick exercise like pushups, walking around the room, taking a stroll outside, or even doing some jumping jacks. Have a habit of eating while watching tv? Try eating something lower calorie like cucumber slices with lemon pepper seasoning, a handful of almonds, or 1 cup of fresh berries. According to recent research from the mayo clinic, diligent exercise, even for small periods of time during the day, can burn several hundred calories more than just doing daily activities like walking, sitting, standing, etc.
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