How chewing food properly can keep you slim

Not only will you eat less, but your body will absorb more nutrients...

LIKe most of us, I suspect, I remember years ago being told to chew my food at least 32 times before swallowing it. It was an idea based on the claims of a 19th- century health food guru in the U.S. called Horace Fletcher — also known as ‘The Great Masticator’, his catchline was: ‘Nature will castigate those who don’t masticate’.

Why 32 times? Perhaps because most human adults have 32 teeth. Fletcher claimed to chew every mouthful 100 times and said that following his approach would turn ‘a pitiable glutton into an intelligent epicurean’.

He suggested that lots of masticating — even when consuming liquids — would not only make you stronger and fitter, but could cure alcoholism, appendicitis, an inflamed gut and even insanity. None of which is true.

But new research has shown there is one surprising benefit to extensive chewing: it can increase your metabolic rate, the amount of energy you burn when at rest, by up to 15 per cent, which is far larger than anyone expected.

In a study at Manchester University, 15 women and six men were asked to chew two types of tasteless gum for 15 minutes: one was soft and the other was hard. The volunteers’ total energy expenditure was carefully monitored while they were chewing.

TO THEIR surprise, the researchers found that when the volunteers were chewing the softer gum, their metabolic rate went up by 10 per cent. Gnawing at the tougher gum, it rose by an even more impressive 15 per cent.

This effect is simply because chewing is hard work. The impact on calories burnt of doing a bit more chewing isn’t huge (roughly like standing up for about 20 minutes), but every little bit helps.

The researchers now plan to do further studies, measuring the impact of chewing real food, such as steak and nuts, on energy expenditure.

It’s not just about the energy we use when we chew: there is also evidence that when we chew more, we eat less. In 2018, Dr Kevin Hall, from the National Institutes of Health in the U.S., conducted a study where 20 healthy volunteers spent four weeks at his lab where they were closely monitored.

For the first two weeks they were randomly allocated either to eating meals that were ultra-processed ( the sort of convenience and other heavily processed foods that contain strange- sounding ingredients and come in bright packages) or eating foods that were minimally processed (i.e. made from scratch).

The volunteers then swapped for the other two weeks.

To give you an idea of what they were fed, an ultra-processed breakfast might consist of a bagel with cream cheese, while the unprocessed breakfast was porridge with bananas, walnuts and milk.

All the meals contained exactly the same balance of calories, sugar, fibre, fat and carbohydrates. The volunteers were told they could eat as much or as little as they wanted of each meal and of snacks, which were readily available.

When the volunteers were eating ultra-processed food, they consumed around 500 calories more per day and gained an average of 0.9kg (2lb) over two weeks.

They lost roughly the same amount when they were on the unprocessed diet.

Why did this happen? Dr Hall is not sure (he’s doing further studies to find out), but he noticed that when the volunteers followed the ultra-processed diet they finished faster, probably because it was softer and easier to swallow without having to do much chewing.

And the faster you eat, the more you eat. Less processed food requires more breaking down in your mouth, so you are forced to chew more and eat more slowly.

one of the first studies to show that the faster you eat, the more you eat, was published in 2008, by the University of rhode Island.

researchers asked 30 young women to eat a series of meals quickly or slowly. When they were eating slowly they not only ate less (579 calories versus 645 calories) but they reported feeling fuller and more satisfied afterwards.

This could be because it takes time for the food you eat to pass through your stomach and reach cells in your small intestine that release a hormone called PYY, which signals to your brain that you are full. If you eat rapidly, and don’t pause to chew and chat, then you will eat more before your brain tells you to stop.

As well as burning extra calories and encouraging you to eat less, more chewing can help you extract more nutrients from your food, particularly if you’re eating tough foods, such as nuts.

In a study in the American Journal of Clinical Nutrition in 2009, 13 healthy adults were asked to chew a handful of almonds ten, 25 or 40 times. They underwent blood tests before and after each chewing session, and their appetites were then monitored for three hours. Poo samples were also taken.

It turned out that the more they chewed, the less hungry the volunteers felt afterwards and the better their blood sugar control was.

While the exact mechanism is unclear, it also turned out that the more they chewed the less nutrients came out in their poo, suggesting that those nutrients had been better absorbed.

So perhaps Horace Fletcher was onto something. Having made a fortune on the lecture circuit, he died of bronchitis at the ripe old age of 69 in 1919, when average life expectancy in the U.S. was just 44.