A recent paper shed light on an under studied factor affecting your your caloric intake: how you chew your food.
The whole paper was fascinating. It gave a group of subjects the same meal, and compared the differences in chewing activity between obese and non-obese people. The paper aimed to shed light on two questions:
1). Do skinny people tend to chew their food differently than obese people?
2). Does the act of chewing itself change the way your food is digested?
Here’s the summary of the results (emphasis added by me):
Compared with lean participants, obese participants had a higher ingestion rate and a lower number of chews per 1 g of food. However, obese participants had a bite size similar to that of lean subjects. Regardless of status, the subjects ingested 11.9% less after 40 chews than after 15 chews. Compared with 15 chews, 40 chews resulted in lower energy intake and postprandial ghrelin concentration and higher postprandial glucagon-like peptide 1 and cholecystokinin concentrations in both lean and obese subjects.
If you don’t feel like processing the results yourself, here are the take away points:
1). Both skinny and obese people have the same bite size, but obese people tend to chew their food less, which increases their ingestion rate and caloric intake.
2). Chewing your food twice as much results in about a 10% reduction in your caloric intake, give or take.
3). More chewing results in a better metabolic hormonal balance after your meal.
The correlation between chewing and reduced caloric intake is encouraging, but it’s important to recognize that the 10% number is probably an upper bound on how much you can reduce your calories. While chewing your food 40 times will reduce your ingested calories by 10%, chewing 60 times is probably probably won’t reduce it by 20%. You can’t chew your way out of everything.
The third point is remarkable. It refers to the last sentence in quote above. There’s a lot of scientific jargon there, but the basic point is that the slower ingestion rate from chewing your food more gives your meal more of a “slow carb” effect independent of the food you’re eating. When sugar enters your body after a meal a slew of metabolic pathways get turned on and off. Lifestyle diseases like diabetes are related the fact that your body’s sensitivity to these on/off switches gets dulled and it starts to lose its ability to process food efficiently, causing all sorts of ancillary side effects. When people chewed their food more the balance of some of these chemicals improved because the food enters your body more slowly.