By SUSAN CALLAHAN, Associate Editor and Featured Columnist
Recently, something happened to me that almost never does --- I lost weight without trying. I had been in one of those periods when you just get tied up in all the business of life . In this instance, the business of life involved getting over the death of a friend and helping her son get through it too. I had decided to not keep track of what I was eating, because, frankly, you can only handle so much, and dieting was a step too far for this particular month. I vowed to get back on track once I had gotten through the crisis.
A month later, I was getting dressed when my sweater just didn't look the same on me. It looked surprisingly comfortable, almost loose fitting. I quickly stepped on the bathroom scales to verify and --yes! -- I had lost almost 10 pounds.
What in the world had I been doing? I quickly did a mental check and the only change I had made was that I had indulged myself every day in one of my favorite comfort foods to deal with the stress --- walnuts. I also threw in peanuts just to change it up some days.
Intrigued by what had happened to me, I did some research on nuts. Could it be that eating the nuts had actually helped me lose weight? Come on, that's...nuts.
Nuts Make You Eat Less Later
Nuts are notoriously rich in calories which is why most of us avoid them when we're trying to lose weight. A cupful of walnuts has 523 calories, a cup of almonds has 529 calories, a cup of pecans has 684 calories and a cup of peanuts has 828 calories.
But that's not the whole story. Nuts cause an effect that scientists call "dietary compensation". When you eat nuts, you later naturally adjust your diet to eat less later.
This dietary compensation means that about 55% to 75% of the extra calories that you get from eating nuts is naturally subtracted from your diet by eating less of other foods, according to a 2008 study. This study, conducted jointly by scientists from Purdue University, Pennsylvania State University and Temple University, was a comprehensive look at all other existing studies on how nuts change our body weight.
Why do we eat less of other foods when we eat nuts? Scientists cannot say why for sure but here are the possible theories. The first is that nuts satisfy us more than other foods. There's something about the high oil content in nuts that triggers a message from the stomach to the brain that says "I am full, eat no more".
Another theory is that the crunchiness, the texture of nuts satisfies the mouth. You may be just tiring out your jaw when you eat nuts and that in and of itself might be another signal to the brain to stop eating.
Finally, nuts have fiber. Fiber is bulky which crowds out available space in your stomach and intestines, again giving your brain the message to stop sending more food down here.
Only Some of the Oil in Nuts Is Digested
We know that nuts are high in fat which should theoretically make them a forbidden food if you are dieting. But what scientists have found is that not all the oil in nuts is actually digested.
Say you eat a handful of peanuts. How much of the handful actually gets digested and taken into your blood stream. Well, the way that scientists measure that is simple though somewhat disgusting. They feed people the nuts as the sole source of fat in their diet and then they measure the fat content of their feces.
Using this method, scientists have come to understand that your body is not very efficient in absorbing the fat from nuts. In fact, from 10% top 15% of all the fat in the nuts you eat never gets digested and instead just passes out your body in your stool.
Why does so much of the nut's oil go undigested? Scientists believe that the answer may be in the toughness of the outer layer of the nut. The intestines simply have a harder time breaking it down and getting to the oil inside.
Much more of the oil is ingested when you eat peanut butter, for example, because the processing of peanuts into peanut butter, all the hard work of breaking down the outer layer has already been done fro you.
If you're keeping track, you can see that the calories loss from eating nuts is so far decreased by between 55% to 75% due to dietary compensation and another 10% to 15% is passed in your stool. That's up to 90% of the calories accounted for. And now for the last 10%.
Eating Nuts Raising Your Resting Energy Expenditure
Numerous studies have found that certain foods are "thermogenic", meaning they raise your body's temperature and make you burn calories. The most thermogenic food is protein.
But nuts are also thermogenic. To digest the calories from nuts, your body had to expend an additional 10% of calories. After you eat nuts, while you are just sitting there, your body is burning extra calories. The Purdue study estimates that on average nuts raise the body's fuel burn by 10%.