Tara Parker-Pope recently wrote an interesting article for her Well Column in the New York Times about the effect of making small changes in diet, like eating one less cookie per day, on weight. Her article was based on a Commentary in JAMA by Martijn Katan and David Ludwig titled "Extra Calories Cause Weight Gain—But How Much?"
She points out that 1lb of fat is equal to about 3500 calories. This means that in order to lose a pound of fat you need a calorie deficit of about 3500 calories. That means you must burn 3500 calories more than you take in.
Interestingly though, to gain a pound of fat, you need to have an excess of about 4000 calories. This is because the process of converting foods is not 100% efficient and on average about 500 calories are needed to create 1lb of fat from the food you eat.
The average daily supply of calories available per person in American is about 1000 calories more than the average person's daily requirements. Based on the previous paragraph, eating an extra 1000 calories per day would lead to a weight gain of 1.75 lbs per week or 91.5lbs per year! However, this is not exactly what happens, because the bodies metabolism and energy requirements change with time and size. So as you gain weight your energy requirements will increase in order to maintain that weight and so you need to eat increasingly more calories to gain more weight.
The same issues come into play when we talk about losing weight. As you lose more weight your energy requirements will decrease, so that in order to maintain weight or lose more weight you must take in even less calories.
I think though that the messages in the NYT and JAMA articles is confusing. But the gist of what they are saying is that figuring out how our caloric intake effect our weight is not a simple equation and therefore gaining and losing weight over time takes more calorie intake or deficit than we might think. Small dietary changes such as cutting out a soda or a cookie from diet isn't going to make a major long term impact on weight, because most people are taking in so many extra calories that they are still going to have an excess of calories and gain weight in the long run. However, it will make a difference, because while you would still gain weight, you will gain less in the end. But if you want to lose weight or maintain weight in the long run its going to take more than just one small changes. It requires multiple small changes that add up to creating no net gain of calories to maintain weight or a net loss of calories to lose weight. The amount of calories taken in will have to change over time because of changes in the bodies metabolism.
What do you think about the effects of small dietary changes on weight?
