Scientists have been debating the cause of obesity. But, unfortunately, they also disagree on the best way to lose weight.
One theory says that food and drink with a lot of carbs make your body produce more insulin. Unfortunately, this makes your fat cells store more calories, which is terrible for your body because there is less energy (from fat cells) in the rest of your body. This results in a person feeling hungry and slowing their metabolism. This causes people to gain weight over time.
Carbohydrates can cause your body to make more insulin than fat. But fat does not cause a spike in insulin levels immediately after a meal. The energy balance model also produces less of a distinction between fat and carbohydrates.
Two scientists, John Speakman from the University of Aberdeen in Scotland and Kevin Hall from the National Institute of Diabetes and Digestive and Kidney Diseases in Maryland, do not say that low-carbohydrate diets are bad. However, they also agree that some people do better with a high-fat diet.
This study looked at 29 different diets for mice. Sixteen of these diets had fixed amounts of protein, while the other thirteen varied the amount of fat and carbohydrate. The study looked at what effect these different diets had on body fat.
The model predicts that if there are more carbohydrates in a diet, there will be higher insulin levels after eating, and this can cause an increase in body fat and an increase in total calories consumed.
But mice that ate high carb diets for 12 weeks or nine years in human life had fewer calories and less fat. As a result, they also gained less weight. The mice still had higher levels of insulin after eating, though.
Studies in Humans
Some people have a diet with 10% carbohydrate and 75% fat. Other people have a diet with 75% carbohydrate and 10% fat. A study was done that looked at the effect of these diets on people who had weight problems. The researchers found that both diets helped reduce weight, but the first group lost more weight than the second group.
The participants were allowed to eat as much or as little food as they wanted. We predicted that the high carbohydrate diet would result in a higher spike in insulin levels following meals based on the carbohydrate-insulin model.
Some people were tested. They were on a high-carb diet, and they ate less than the low-carb dieters. However, they also said that they felt as satisfied as to the other group, which must have been true because they ate less food.
Only the high carb diet resulted in a significant loss of body fat. Speakman and Hall argue that insulin affects many organs around the body, not just after mealtimes. They write that insulin’s role in regulating body fat is best understood as part of a dynamic network of factors controlling and mediating the effects of energy imbalance.
For example, they say high insulin levels, combined with signals from fat tissue, tell the brain to reduce energy intake when there is too much body fat.
Dr. Ludwig, a professor of nutrition at Harvard School of Public Health in Boston, MA, is not happy with the study. He said that it was “strongly biased” because the low-carb diets contained large amounts of saturated fat from meat.
Dr. Ludwig said that saturated fat causes severe inflammation and metabolic dysfunction in rodents, which means it is hard to tell if this model applies to people or not because those who are eating the low-carb diet are unhealthy too.
He said that other studies have shown that rodents who eat high-carb diets rapidly get fat. He also challenged the validity of short studies in humans, such as the 2-week study cited by Speakman and Hall. These do not give the body enough time to adapt to changes in food.
His analysis says that more extended studies consistently show higher energy expenditure on low-carb diets (keto). In addition, several reviews of clinical trials have shown that low carb, high fat keto diets promote weight loss.
Prof. Naveed Satar from the Institute of Cardiovascular and Medical Science at the University of Glasgow in the U.K. told us that low-carb diets could help people lose weight.
However, he thinks it is because they eat less food, but not because of how some people feel about how carbs affect insulin levels. “People who go on low carb diets tend to eat less as they increase protein intake, which tends to suppress appetite a little,” he said.
He said that his research suggests that people with more weight get most of their calories from fat rather than sugar. So, along with eating fewer calories, you also need to cut down on the amount of fat you eat.