The question of the difference between fasting and caloric restriction comes up very often. Many caloric advocates believe that fasting works precisely because you limit the amount of calories you eat. So they argue that what matters is the average, not the frequency. It has nothing to do with the truth. If we compare a week with light rainfall with a week when the sun shines for 6 days and it rains heavily for one day, the average will be the same, right?
So why assume that cutting 300 calories a day for a week will have the same effect as reducing 2,100 calories in one day?
For both type 2 diabetes and the desire to lose weight, the constant calorie reduction strategy is the most common approach recommended by dietary authorities. Its supporters say cutting 500 calories a day will burn about 0.5 kg a week.
The American Diabetes Association recommends focusing on “diet and exercise to achieve an energy deficit of 500 – 750 kcal/day.” This is an approach that has been used for 50 years and is based on the reduction over the day. Nutritionists often recommend eating 4, 5, or 6 meals a day. The menus contain information about calories, there are tons of calorie counting apps, thousands of books have been written about it, and yet most people fail to win with obesity.
This approach was probably tried by anyone who wanted to lose a few pounds. Data from the UK shows that by following these rules, only 1 in 210 obese men and one in 124 women were successful. That’s less than 0.5%. This strategy simply won’t work because it slows down your metabolism.
Diets based on the “eat less, more exercise!” usually provide 1,200 – 1,500 calories a day, which meets about 70% of the body’s needs with increased physical exertion. Initially, this has an effect, but the resting metabolic rate drops very quickly. The body slows down to adapt to the amount of calories it receives. After it has adjusted, the weight returns to normal.
The slowdown in metabolism was scientifically proven over 50 years ago. Dr. Ancel Key of Minnesota introduced a diet of 1,500 calories a day in the study group, which was a 30% reduction. That’s how their metabolic rate dropped. The volunteers felt bad, tired, and hungry. After returning to the original diet, the weight of the respondents also returned to the previous level.
The key to success is maintaining your basal metabolic rate, which is achieved by intermittent fasting. Its use causes several hormonal reactions that do not occur in the case of caloric reduction – the level of insulin decreases, the level of norepinephrine increases, maintaining the metabolic rate at a high level. The level of growth hormone also increases, allowing the maintenance of lean muscle mass.
During fasting, the body uses stored fat. Metabolism remains unchanged, only the source from which the energy is drawn changes. The glycogen stored in the liver is burned first. When this is over, fat is burned. The body stores it in large amounts, so there is no reason for your metabolic rate to drop. This is the difference that makes fasting effective and reducing calories not.
Hormonal changes during fasting are completely different than after reducing calories. Reducing insulin levels and resistance to its effects in intermittent fasting is crucial.
The phenomenon of immunity is not only associated with hyperinsulinemia but also with constantly elevated insulin levels. The intermittent nature of fasting prevents the occurrence of resistance to its effects.
Studies have been conducted that compared the effect of constant calorie reduction with the effect of intermittent fasting while maintaining the same average amount of calories consumed per week. The study used a Mediterranean diet with an average of 30% fat. However, in the first group, the amount of calories was reduced to the same extent throughout the week, while in the second group, the amount of calories was strongly reduced only for 2 days a week.
After 6 months, the weight and percentage of body fat were the same for both groups. However, there were significant hormonal differences. Insulin levels, which is the main cause of insulin resistance (and obesity over an extended period of time), fell initially in the first group but stopped quickly.
The insulin level in the second dropped further. Intermittent fasting improved insulin sensitivity, despite consuming the same amount of calories. This is why, unlike reducing calories, it will be effective in type 2 diabetes.
A similar study was conducted quite recently. (https://www.ncbi.nlm.nih.gov/pubmed/27569118) The first group reduced the daily calories consumed by 400. The other one ate every other day. The research lasted six months.
What conclusions emerged after their completion? First of all, intermittent fasting is a safe and effective method. In terms of weight loss, it fared better, although the differences were minimal. However, the devil is in the details. The dangerous visceral fat reduction was 2 times greater, and the overall fat reduction was 6 times greater.
Many people are concerned about “burning muscles” with intermittent fasting. This is contradicted by the results of the cited studies, which show that intermittent fasting increased lean muscle mass by 2.2%. Calorie reduction – only by 0.5%. This means that fasting is more than four times more effective in preserving muscle mass. Myth busted.
What happens to the metabolic rate that determines your long-term success? The resting metabolic rate decreased by 76 calories per day for the calorie reduction group. The intermittent fasting group saw a decrease of only 29 calories. In other words, cutting calories slows down your metabolism two and a half times more than fasting!
Fasting has been used to control obesity almost always. Meanwhile, the method of reducing calories has only been known for several decades and in the overwhelming majority of cases, it ends in failure.
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