woohat if I told you all you have to do to lose weight is read a calendar and tell the time? These are the basics for successfully following an intermittent fasting diet.
Could it be that simple, though? Does it work? And what is the scientific basis of fasting? As a registered dietitian and expert in human nutrition and metabolism, I am frequently asked such questions.
Simply put, intermittent fasting is defined as alternating periods of fasting in which eating is allowed. One way is alternate day fasting. On “fast days,” adherents of this form of fasting are restricted to consuming more than 500 calories per day; On “feast days”, which are every other day, they can eat freely, without restriction on the type or amount of food eaten.
Other methods include the increasingly popular 5:2 method. This form of fasting includes a five-day feast and two days of fasting per week.
Another variation relies on time-restricted eating. This means adherents must fast for a specified number of hours – typically 16 to 20 per day – while freely consuming foods within a specified four to eight hour period.
But what about having breakfast and then small meals throughout the day to keep the body’s metabolism going? After all, this is the conventional wisdom many of us grew up with.
To answer these questions, it helps to understand the basics of human metabolism.
Human Metabolism 101
The human body needs a constant supply of energy to sustain life, and the foods we eat provide us with this energy. But because eating is often followed by a period of time without eating, a complex set of biological pathways take place to meet the body’s energy demands between meals.
Most pathways function at some level all the time, but they fluctuate after a meal in a predictable pattern known as a fed-fast cycle. The cycle time frame can vary depending on the type of food eaten, the size of the meal, and the person’s activity level.
So what happens, metabolically, after we eat? Consumption of carbohydrates and fats causes an increase in blood sugar as well as levels of lipids, including cholesterol and triglycerides.
This triggers the release of insulin from the pancreas. Insulin helps tissues throughout the body take up glucose and lipids, which supply energy to the tissues.
Once energy needs are met, the remaining glucose is stored in the liver and skeletal muscle in a condensed form called glycogen. When glycogen stores are full, the excess glucose is converted into fatty acids and stored in adipose tissue.
About three to 18 hours after a meal — again, depending on a person’s activity level and the size of the meal — the amount of circulating blood sugar and lipids return to baseline levels. So the tissues must then rely on fuel sources already in the body, which are glycogen and fat. A hormone called glucagon, secreted by the pancreas, helps facilitate the breakdown of glycogen and fat to provide the body with energy between meals.
Glucagon also initiates a process called gluconeogenesis, which is the synthesis of glucose from non-dietary sources. It helps in maintaining the correct level of blood sugar level.
When the body reaches a true fasting state—about 18 hours to two days without additional food—the body’s stores of glycogen are depleted, and tissues such as the heart and skeletal muscle begin to rely heavily on fat for energy. seem. This means an increase in the breakdown of stored fat.
“Ahh!” you may say. “So is intermittent fasting the key to the ultimate fat burning?” Well, it’s not that easy. Let us know what happens next.
Read also: Can you lose weight by not eating after 8 pm? What the Diet Industry Won’t Tell You
state of starvation
Although many tissues adapt to use fat for energy, the brain and red blood cells require a constant supply of glucose. But when glucose is not available due to fasting, the body starts breaking down its own proteins and in turn converts them into glucose. However, because proteins are also important to support essential bodily functions, this is not a permanent process.
When the body enters a state of starvation, the body goes into self-preservation mode, and a metabolic shift occurs in an attempt to save the body’s proteins. The body continues to synthesize glucose for the cells and tissues that need it, but the breakdown of stored fat also increases to provide energy to tissues such as skeletal muscle, heart, liver and kidneys.
It also promotes ketogenesis, or the formation of ketone bodies – molecules produced as an energy source in the liver when glucose is not available. In a state of starvation, ketone bodies are important energy sources, as the body is simply not able to use fat for energy. This is why it is wrong when some proponents of intermittent fasting claim that fasting is a way to burn “only fat” – this is not biologically possible.
What happens when you break the fast? The cycle starts again. Blood glucose and lipids return to basal levels, and energy levels in the body are maintained seamlessly by transitioning between the metabolic pathways described earlier. The neat thing is that we don’t even have to think about it. The body is well equipped to adapt between periods of feasting and fasting.
If the “all-or-nothing” diet approach to weight loss sounds appealing to you, chances are it could work. In fact, intermittent fasting diets have produced a clinically significant amount of weight loss. Intermittent fasting may also reduce disease risk by lowering blood pressure and blood lipid levels.
On the other hand, several studies have shown that weight loss from an intermittent fasting diet is no greater than weight loss on a standard calorie-restricted diet.
In fact, the weight loss caused by intermittent fasting is not due to spending time in some kind of magical metabolic window, but to reducing overall calorie consumption. On feast days, dieters usually do not fully compensate for the lack of food on fasting days. That results in mild to moderate weight loss. About 75% of the weight is fat mass; The rest is lean mass. That’s about the same proportion as a standard low-calorie diet.
If you still want to do intermittent fasting, there are a few things to keep in mind. First, there have been no studies on the long-term safety and efficacy of following this type of diet. Second, studies show that intermittent fasters don’t get enough nutrients.
Exercise is something else to consider. It helps maintain lean muscle mass and may also contribute to weight loss and long-term weight maintenance. This is important, as about a quarter of the weight on any given diet is muscle tissue, and the efficacy of intermittent fasting for weight loss has only been demonstrated for short periods.
Also, once you stop following the intermittent fasting diet, your weight is very likely to come back. This is an important consideration, as many people find it difficult to follow the diet for long periods of time. Imagine the challenge of planning six months’ worth of feasting and fasting around family dinners, holidays and parties. Then imagine doing it for the rest of your life.
Ultimately, the best approach is to follow an eating plan that meets current dietary recommendations and fits your lifestyle.
McCall Montgomery, assistant professor of nutritional sciences, Oklahoma State University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Read also: Intermittent fasting is a fad with benefits but the science behind it demands more answers