Obesity: It's Not Just What You Eat, But When You Eat
According to the World Health Organization (WHO), the worldwide obesity rate has almost tripled since 1975. Global data from 2016 showed that 39% of adults were overweight and 13% were obese, meaning that over 1 in 10 adults in the world is obese. In the United States, however, over 1 in 3 adults is obese, a value much greater than the global rate. Obesity occurs because of an abnormal and unhealthy accumulation of fat in the body. It is clinically diagnosed when a person has a body mass index (BMI) of 30 or more. Obesity can increase the risk of having other diseases, including heart disease, stroke, and type 2 diabetes, which make up some of the leading causes of death worldwide. Because of this, understanding the causes, and more importantly, the prevention of obesity is the focus of many studies today. Although it is already well understood how diet and exercise contribute to fat accumulation, recent research indicates that the timing of meals also plays a significant role in obesity.
This new insight comes from a team of researchers at Vanderbilt University. Previous research has suggested the importance of the timing of meal consumption in mice. Mice fed high-fat diets during their waking periods maintain healthy weights, while mice fed the same diet during their sleeping periods gain significantly more weight. However, whether a similar effect occurs in humans was not known, so the Johnson Lab at Vanderbilt University sought to explore a potential correlation between weight gain and mealtimes in humans. In their experiment, the researchers made use of an innovative whole-room calorimetry chamber, a controlled room where subjects can temporarily live. The room measures their oxygen uptake and carbon dioxide production, which are important indicators of how food is metabolized and stored in the body. Thus, it is possible to measure the rate at which lipids or carbohydrates break down.
To simulate typical eating habits, the researchers created two conditions, one where participants ate breakfast, lunch, and dinner, and another where the same participants ate lunch, dinner, and a late-evening snack. The latter group represented those who skip breakfast and have a late-night snack instead—a common habit. The meals provided to the subjects in both conditions were identical in calorie content and nutritional value, with the only difference being the times at which they were offered. Moreover, there was no difference in activity level between the subjects in either group. This way, any metabolic changes found in the chamber could be attributed to the variations in mealtime.
This new insight comes from a team of researchers at Vanderbilt University. Previous research has suggested the importance of the timing of meal consumption in mice. Mice fed high-fat diets during their waking periods maintain healthy weights, while mice fed the same diet during their sleeping periods gain significantly more weight. However, whether a similar effect occurs in humans was not known, so the Johnson Lab at Vanderbilt University sought to explore a potential correlation between weight gain and mealtimes in humans. In their experiment, the researchers made use of an innovative whole-room calorimetry chamber, a controlled room where subjects can temporarily live. The room measures their oxygen uptake and carbon dioxide production, which are important indicators of how food is metabolized and stored in the body. Thus, it is possible to measure the rate at which lipids or carbohydrates break down.
To simulate typical eating habits, the researchers created two conditions, one where participants ate breakfast, lunch, and dinner, and another where the same participants ate lunch, dinner, and a late-evening snack. The latter group represented those who skip breakfast and have a late-night snack instead—a common habit. The meals provided to the subjects in both conditions were identical in calorie content and nutritional value, with the only difference being the times at which they were offered. Moreover, there was no difference in activity level between the subjects in either group. This way, any metabolic changes found in the chamber could be attributed to the variations in mealtime.
Image Source: Pexels
The researchers in the Johnson Lab then found that subjects with the late-evening snack diet had significantly less overall lipid oxidation, or fat breakdown, throughout the experiment than subjects with the breakfast diet. When people sleep, their circadian rhythm causes a metabolic shift from mainly carbohydrate oxidation to lipid oxidation. However, late-evening snacking delayed this shift in the study, leading to an average decrease of 15 grams of lipids less burned each day. Lipids that are not oxidized accumulate as fat tissue instead.
Accumulation of visceral fat within the abdomen can have detrimental effects on health, as it is linked to obesity-related diseases like diabetes and heart disease. Therefore, the researchers suggest that efforts to prevent obesity should include not only a healthy diet and exercise, but also a focus on when people eat their meals. Specifically, avoiding snacking after evening meals can cause a significant decrease in daily fat accumulation. As researchers continue to examine meal times and other previously overlooked factors connected to obesity, efforts to reverse the obesity epidemic can become more targeted, efficient, and effective.
Accumulation of visceral fat within the abdomen can have detrimental effects on health, as it is linked to obesity-related diseases like diabetes and heart disease. Therefore, the researchers suggest that efforts to prevent obesity should include not only a healthy diet and exercise, but also a focus on when people eat their meals. Specifically, avoiding snacking after evening meals can cause a significant decrease in daily fat accumulation. As researchers continue to examine meal times and other previously overlooked factors connected to obesity, efforts to reverse the obesity epidemic can become more targeted, efficient, and effective.
Image Source: Pixabay
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