Remember how your mom would always tell you to chew your food? She spoke wisely. Proper chewing of your food not only helps to break down the food mechanically, but also helps to release more digestive-system enzymes to carry the process further. If you don't chew your food enough, it may result in incomplete digestion. That means there are less nutrients, such as amino acids, getting to your muscles, and this could limit your muscle growth.
According to research from Japan, the rate at which you eat your meals may influence the amount of bodyfat you hold. Researchers from the National Institute of Health and Nutrition in Tokyo assessed the eating rate and the amount of food eaten by almost 1,700 female subjects along with their body mass index (the BMI is a way to determine obesity based on weight and height). They reported in a 2003 issue of International Journal of Obesity and Related Metabolic Disorders that the faster the subjects tended to eat their meals, the higher their BMI and, therefore, their body fatness.
In another study, researchers from Nagoya University Graduate School of Medicine (Aichi) assessed the eating rate and the amount of food eaten by about 2,700 male and almost 800 female subjects, along with their BMI and blood glucose and insulin levels. They reported in a 2008 issue of Preventive Medicine that not only did the faster eaters have higher bodyfat, but they had higher blood glucose and insulin levels than those who ate slower.
The take-home message from these studies is that eating your meals slowly can help you build more muscle mass and keep bodyfat at bay. So slow down, enjoy your meal, and chew each bite thoroughly to start the digestion process and keep insulin levels low.
References: R. Otsuka et al., "Eating fast leads to insulin resistance: Findings in middle-aged Japanese men and women," Preventive Medicine, 46(2):154-59, 2008; S. Sasaki et al., "Self-reported rate of eating correlates with body mass index in 18-year-old Japanese women," International Journal of Obesity and Related Metabolic Disorders, 27(11):1405-10, 2003.