Can chewing more help you lose weight?
Chewing more thoroughly can improve your digestion and make your food more nutritious. It can also help with weight loss. Plus: a follow-up question on artificial sweeteners and the microbiome.
Nutrition Diva is hosted by Monica Reinagel. A transcript is available at Simplecast.
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Hello and welcome to the Nutrition Diva podcast. I’m your host, Monica Reinagel, and today I have some new research on an age-old question: How does chewing affect your nutrition?
But first, I wanted to answer a question from Sonja in regard to my recent episode on artificial sweeteners. She writes:
“After listening to your recent podcast about artificial sweeteners, I’ve finally decided to try to kick my addiction to artificially sweetening everything. If I've been having a lot of artificial sweetener and now cut it out of my diet, how long will it take for my gut microbiome to repair itself?”
The good news is that the gut microbiome responds relatively quickly to changes in the diet. Although I have not seen research on exactly this question (that is, how fast changes in artificial sweetener intake changes the microbiome), other research shows that changes in the diet (such as decreasing meat or increasing vegetables and whole grains) can alter the makeup of the microbiome in just a few days.
Of course, if you want those changes to be sustained, then those dietary changes need to be sustained as well!
And now, here’s a question from Heather about chewing:
“A lot of magazine and internet articles recommend chewing each bite of food 30, 40, even up to 80 times. Supposedly, increasing the number of times will help you lose weight. There is even an iPhone app that will track your chews. A colleague of mine also claims there are nutritional benefits to chewing your food extremely well. Is any of this true?”
Although this does sound like one of those nutritional urban legends I’m always debunking, chewing your food more thoroughly can improve digestion, promote weight loss, and affect the nutritional value of foods—in ways you might not expect.
Digestion does not begin in the stomach but in your mouth—and chewing your food more thoroughly can improve digestion. First, digestive enzymes in your saliva break down starches into simple sugars. In fact, if you chew on a saltine cracker or a bit of bread long enough, it will actually start to taste sweet. By chewing for one minute, up to half of the starch may be digested before you even swallow!
Your saliva also contains some fat-digesting enzymes that help begin the process of breaking down the fats in your food. The act of chewing food—including the stimulation of your taste and smell receptors—also triggers the production of stomach acid and pancreatic juices further along the digestive tract, so that the system is primed for the whole digestive sequence.
Finally, chewing well breaks the food down into smaller pieces, so when you swallow the food, it mixes more thoroughly with stomach acid. Stomach acid starts to break down food proteins into smaller, more digestible molecules and also kills bacteria and other pathogens that may be in your food. The more surface area that is exposed to stomach acid, the more effectively it can do its job.
By the way, chewing well can have beneficial effects on the other end of the digestive process as well. Thorough chewing means that less un- or partially-digested food matter enters your colon and that translates into less intestinal gas.
If you’re digesting your food better, does that mean that you get more nutrition from it? Yes! Longer chewing has been shown to increase the amount of protein your body can absorb from foods and put to use building muscle. It also makes some vitamins and minerals more available for absorption—especially from uncooked fruits and vegetables. (Cooking foods has some of the same nutrient-releasing effects as thorough chewing.) Chewing also increases the amount of fat that is absorbed from foods that contain both fat and fiber, such as nuts.
But wait a minute. This whole chewing thing seems to be taking an unexpected turn. Does improved digestion and absorption mean that you’ll end up getting more calories from your food? Actually, it does. I’m afraid I can’t quantify exactly how many more calories you might absorb by chewing well—although I don’t think it’s enough to get too excited about.
And there’s one more thing to consider: Converting more of the starches into simple sugars by chewing foods more thoroughly can also increase the glycemic index of food. I’ve talked about glycemic index in previous articles but in a nutshell, this means that well-chewed bread or pasta would cause a higher rise in blood sugar than poorly chewed starches.
Despite all of this, chewing more thoroughly appears to have a positive net effect on weight loss through several different mechanisms.
Chewing is a physical activity involving muscles and, like any other physical activity, it burns calories. But not very many. Researchers writing last month in the journal Science Advances found that chewing increases your energy expenditure by 10 to 20%. However, for the average person who spends about 35 minutes a day chewing, this adds up to fewer than 10 calories per day.
But these researchers also found that eating stiffer or harder foods burns 50% more energy than soft foods. Several of the researchers involved in this study are actually anthropologists, and they were interested in the way that human metabolism and physiology co-evolved with changes in our food supply, such as the advent of cooking, which makes foods softer and easier to chew.
Whereas chewing accounts for less than 1% of the modern human’s daily energy expenditure, it may have cost our prehistoric ancestors, who were gnawing on bones, gristle, and raw plant matter, 2-3 times as much energy to nourish themselves.
Modern processing methods take this another giant step further, of course, making it possible to consume ever larger quantities of food and calories with less chewing. Our metabolisms and physiology are still evolving, of course, but much more slowly than our food supply is.
We know that people who eat more minimally processed foods end up taking in substantially fewer calories than those who eat highly processed foods—and part of it could be that minimally processed foods simply require more time and effort to bite and chew.
Chewing more means you eat a lot more slowly—and this gives the hormones that signal satiation, or fullness, a chance to reach your brain before you’ve polished off the entire contents of the buffet.
Studies have found that taking smaller bites and chewing them longer can decrease your food intake at a meal by as much as one-third. Obviously, this more than compensates for a couple of extra calories that all that chewing might release. And eating smaller portions also has a much more profound impact on your blood sugar levels than the change in a food’s glycemic index as a result of the extra chewing.
To sum up, chewing your food more thoroughly can improve your digestion and make your food more nutritious. The extra chewing may burn a few extra calories but, more importantly, will help you control your intake. It may also enhance your appreciation and enjoyment of the food.
There’s no specific number of times that you must chew each bite and some foods require more than others. But with most of us chewing each bite of food just 5 to 7 times, we could probably all benefit from slowing down and chewing more thoroughly.
There’s a simple little trick that we use in the Weighless Program to help with this. Most of us, after taking a bite of food, immediately start loading up the next forkful and even begin lifting it to our mouths, while we’re still chewing the bite we just took. This tends to result in our chewing less thoroughly, swallowing prematurely, and eating more quickly.
We suggest implementing a “mouth full, fork empty” policy. If there’s food in your mouth, your fork should remain empty until you’ve swallowed that bite of food. Try it and see what you think. I’d be interested to hear from you. And if you want to learn more about what else we do in the Weighless Program, you can find out more at weighless.life