McKale Montgomery, Assistant Professor of Nutritional Sciences, Oklahoma State University
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Intermittent fasting could have an array of health benefits, but as of yet there are no long-term studies into its effects. neirfy/iStock via Getty Images Plus
What if I told you all you need to do to lose weight is read a calendar and tell time? These are the basics for successfully following an intermittent fasting diet.
Can it be that simple, though? Does it work? And what is the scientific basis for fasting? As a registered dietitian and expert in human nutrition and metabolism, I am frequently asked such questions.
Simply stated, intermittent fasting is defined by alternating set periods of fasting with periods in which eating is permitted. One method is alternate-day fasting. On “fast days,” followers of this form of fasting are restricted to consuming no more than 500 calories per day; on “feast days,” which occur every other day, they can eat freely, with no restrictions on the types or quantities of foods eaten.
Other methods include the increasingly popular 5:2 method. This form of fasting involves five days of feasting and two days of fasting per week.
Another variation relies on time-restricted eating. That means followers should fast for a specified number of hours – typically 16 to 20 per day – while freely consuming foods within a designated four- to eight-hour period.
To answer these questions, it helps to understand the basics of human metabolism.
Human metabolism 101
The human body requires a continual supply of energy to sustain life, and the foods we eat provide us with this energy. But because eating is often followed by periods of time without eating, an intricate set of biological pathways is in place to meet the body’s energy demands between meals.
Most of the pathways function at some level all the time, but they fluctuate following a meal in a predictable pattern called the fed-fast cycle. The time frames of the cycle can vary, depending on the food types eaten, the size of the meal and the person’s activity level.
So what happens, metabolically speaking, after we eat? Consuming carbohydrates and fats leads to a rise in blood glucose and also lipid levels, which include cholesterol and triglycerides.
This triggers the release of insulin from the pancreas. The insulin helps tissues throughout the body take up the glucose and lipids, which supplies the tissues with energy.
Once energy needs are met, leftover glucose is stored in the liver and skeletal muscle in a condensed form called glycogen. When glycogen stores are full, excess glucose converts to fatty acids and is stored in fat tissue.
About three to 18 hours after a meal – again, depending upon a person’s activity level and size the of the meal – the amount of circulating blood glucose and lipids returns to baseline levels. So tissues then must rely on fuel sources already in the body, which are the glycogen and fat. A hormone called glucagon, secreted by the pancreas, helps facilitate the breakdown of glycogen and fat to provide energy for the body between meals.
Glucagon also initiates a process known as gluconeogenesis, which is the synthesis of glucose from nondietary sources. This helps maintain the right level of blood glucose levels.
When the body reaches a true fasting state – about 18 hours to two days without additional food intake – the body’s stores of glycogen are depleted, and tissues like the heart and skeletal muscle start to rely heavily on fats for energy. That means an increase in the breakdown of the stored fats.
“Aha!” you might say. “So intermittent fasting is the key to ultimate fat burning?” Well, it’s not that simple. Let’s go through what happens next.
The starvation state
Though many tissues adapt to using fats for energy, the brain and red blood cells need a continual supply of glucose. But when glucose is not available because of fasting, the body starts to break down its own proteins and converts them to glucose instead. However, because proteins are also critical for supporting essential bodily functions, this is not a sustainable process.
When the body enters the starvation state, the body goes into self-preservation mode, and a metabolic shift occurs in an effort to spare body protein. The body continues to synthesize glucose for those cells and tissue that absolutely need it, but the breakdown of stored fats increases as well to provide energy for tissues such as the skeletal muscle, heart, liver and kidneys.
This also promotes ketogenesis, or the formation of ketone bodies – molecules produced in the liver as an energy source when glucose is not available. In the starvation state, ketone bodies are important energy sources, because the body is not capable of solely utilizing fat for energy. This is why it is inaccurate when some proponents of intermittent fasting claim that fasting is a way of burning “just fat” – it’s not biologically possible.
What happens when you break the fast? The cycle starts over. Blood glucose and lipids return to basal levels, and energy levels in the body are seamlessly maintained by transitioning between the metabolic pathways described earlier. The neat thing is, we don’t even have to think about it. The body is well-equipped to adapt between periods of feasting and fasting.
Possible downsides
If an “all-or-nothing” dietary approach to weight loss sounds appealing to you, chances are it just might work. Indeed, intermittent fasting diets have produced clinically significant amounts of weight loss. Intermittent fasting may also reduce disease risk by lowering blood pressure and blood lipid levels.
On the flip side, numerous studies have shown that the weight reduction from intermittent fasting diets is no greater than the weight loss on a standard calorie-restricted diet.
In fact, the weight loss caused by intermittent fasting is due not to spending time in some sort of magic metabolic window, but rather to reduced overall calorie consumption. On feast days, dieters do not typically fully compensate for lack of food on fasted days. This is what results in mild to moderate weight loss. Approximately 75% of the weight is fat mass; the rest is lean mass. That’s about the same ratio as a standard low-calorie diet.
Should you still want to go forward with intermittent fasting, keep a few things to keep in mind. First, there are 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 of certain nutrients.
Exercise is something else to consider. It helps preserve lean muscle mass and may also contribute to increased weight loss and long-term weight maintenance. This is important, because nearly a quarter of the weight lost on any diet is muscle tissue, and the efficacy of intermittent fasting for weight loss has been demonstrated for only short durations.
Also, once you stop following an intermittent-fasting diet, you will very likely gain the weight back. This is a critical consideration, because many people find the diet difficult to follow long-term. Imagine the challenge of planning six months’ worth of feasting and fasting around family dinners, holidays and parties. Then imagine doing it for a lifetime.
Ultimately, the best approach is to follow an eating plan that meets current dietary recommendations and fits into your lifestyle.
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McKale Montgomery receives funding from the National Institutes of Health.
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De Visu // Shutterstock
Intuitive eating is the latest anti-diet diet craze, purporting to shift the wellness focus off weight loss and onto forming healthy relationships between the body, mind, and food. Instead of labeling food as good or bad and trying to ignore hunger pangs, its simple philosophy is to eat when you’re hungry and stop when you’re not. The key is staying in tune with your body so you know when you feel full and step away. Rather than forbidding certain foods, intuitive eaters accept that one snack or meal likely won’t upend your health; what matters is sticking to mindful eating habits consistently over time.
The trend follows the growing appetite for health plans that eschew goal weights in favor of overall wellness. But separating truly intuitive eating out from other dieting platforms that tout the concept while pushing restrictive food plans can be wildly complicated for the average person looking to get healthier in 2022.
To explore the science behind the newest anti-diet diet, Almond Cow used scientific studies and news articles to explore Americans’ changing relationship with diet culture and the multiple facets of healthiness people can consider instead.
Nearly half of all American adults reported putting on extra weight during COVID-19, with the American Psychological Association reporting that a full 42% of those who gained weight averaged a 29-pound increase between March 2020 and February 2021. Diet companies and weight-loss subscription services responded with fine-tuned marketing campaigns designed to attract fresh segments of the population, selling an anti-diet lifestyle over a sense of restriction. The play worked: Mobile weight-loss company Noom, for example, riding high on a promise of weight loss without restrictive eating, grew its annual revenue from $237 million to $400 million in 2020 and was on track to exceed $600 million in revenue in 2021.
But when it comes to health and weight, continuing research is demonstrating that dieting doesn’t offer long-term weight loss and can even be harmful to people’s physical and mental well-being. Some of today’s most popular diet programs feed into the intuitive eating concept in which a person theoretically eats when they’re hungry and stops when they’re full. Espousing body positivity and wellness, Found, WW, Noom, and others capitalize on a cultural hunger for more inclusivity and representation across all demographics, ages, genders, and sizes. Yet as many as 95% of people who diet gain the weight back regardless of which method they follow.
So what gives?
Medical experts point to lifestyle as being the most important element of sustained, healthy weight loss. The CDC emphasizes long-term changes over fast-track diets that are designed to drop the most pounds in the shortest amount of time. More Americans are paying attention to all areas of their health, including how much sleep they get a night, their mental health, their hydration, and their stress levels: things that have long been overlooked. Many people are also looking at truly intuitive eating, which studies have shown to have positive outcomes both mentally and physically.
Keep reading to learn more about the actual science behind the anti-diet diet, from the flaws in BMI to healthy habits that matter as much as food intake.
Content warning: This article mentions eating disorders and restrictive dieting.
De Visu // Shutterstock
Intuitive eating is the latest anti-diet diet craze, purporting to shift the wellness focus off weight loss and onto forming healthy relationships between the body, mind, and food. Instead of labeling food as good or bad and trying to ignore hunger pangs, its simple philosophy is to eat when you’re hungry and stop when you’re not. The key is staying in tune with your body so you know when you feel full and step away. Rather than forbidding certain foods, intuitive eaters accept that one snack or meal likely won’t upend your health; what matters is sticking to mindful eating habits consistently over time.
The trend follows the growing appetite for health plans that eschew goal weights in favor of overall wellness. But separating truly intuitive eating out from other dieting platforms that tout the concept while pushing restrictive food plans can be wildly complicated for the average person looking to get healthier in 2022.
To explore the science behind the newest anti-diet diet, Almond Cow used scientific studies and news articles to explore Americans’ changing relationship with diet culture and the multiple facets of healthiness people can consider instead.
Nearly half of all American adults reported putting on extra weight during COVID-19, with the American Psychological Association reporting that a full 42% of those who gained weight averaged a 29-pound increase between March 2020 and February 2021. Diet companies and weight-loss subscription services responded with fine-tuned marketing campaigns designed to attract fresh segments of the population, selling an anti-diet lifestyle over a sense of restriction. The play worked: Mobile weight-loss company Noom, for example, riding high on a promise of weight loss without restrictive eating, grew its annual revenue from $237 million to $400 million in 2020 and was on track to exceed $600 million in revenue in 2021.
But when it comes to health and weight, continuing research is demonstrating that dieting doesn’t offer long-term weight loss and can even be harmful to people’s physical and mental well-being. Some of today’s most popular diet programs feed into the intuitive eating concept in which a person theoretically eats when they’re hungry and stops when they’re full. Espousing body positivity and wellness, Found, WW, Noom, and others capitalize on a cultural hunger for more inclusivity and representation across all demographics, ages, genders, and sizes. Yet as many as 95% of people who diet gain the weight back regardless of which method they follow.
So what gives?
Medical experts point to lifestyle as being the most important element of sustained, healthy weight loss. The CDC emphasizes long-term changes over fast-track diets that are designed to drop the most pounds in the shortest amount of time. More Americans are paying attention to all areas of their health, including how much sleep they get a night, their mental health, their hydration, and their stress levels: things that have long been overlooked. Many people are also looking at truly intuitive eating, which studies have shown to have positive outcomes both mentally and physically.
Keep reading to learn more about the actual science behind the anti-diet diet, from the flaws in BMI to healthy habits that matter as much as food intake.
Content warning: This article mentions eating disorders and restrictive dieting.
Canva
Despite being proven to be deeply flawed, body mass index is a health metric often used as a way to indicate whether someone is overweight.
In fact, the person that invented BMI, Lambert Adolphe Jacques Quetelet, wasn’t even a physician—he was a Belgian astronomer and mathematician. To offer the government an easy solution for calculating obesity, Quetelet created an overly simplistic method: a person’s weight divided by their height squared. As a result, BMI can cause taller people to believe they are more overweight than they are and shorter people to believe they are smaller. Some scientists believe that a waist-to-height ratio is far more accurate in determining obesity.
Canva
Despite being proven to be deeply flawed, body mass index is a health metric often used as a way to indicate whether someone is overweight.
In fact, the person that invented BMI, Lambert Adolphe Jacques Quetelet, wasn’t even a physician—he was a Belgian astronomer and mathematician. To offer the government an easy solution for calculating obesity, Quetelet created an overly simplistic method: a person’s weight divided by their height squared. As a result, BMI can cause taller people to believe they are more overweight than they are and shorter people to believe they are smaller. Some scientists believe that a waist-to-height ratio is far more accurate in determining obesity.
Canva
In many cases, diets are simply ineffective when it comes to losing weight. In fact, diets can actually have the opposite effect by slowing the metabolism down on top of causing more hunger. On top of that, diets can do more harm than good.
Research shows that dieting can have a negative impact on hormones and memory. Instead, scientists are finding intuitive eating to be a far healthier and more effective approach.
Canva
In many cases, diets are simply ineffective when it comes to losing weight. In fact, diets can actually have the opposite effect by slowing the metabolism down on top of causing more hunger. On top of that, diets can do more harm than good.
Research shows that dieting can have a negative impact on hormones and memory. Instead, scientists are finding intuitive eating to be a far healthier and more effective approach.
Rawpixel.com // Shutterstock
Unfortunately, restrictive dieting has harmed many people’s views on food, negatively impacted their health, and even caused eating disorders.
Studies on intuitive eating, however, are showing that this method helps people form healthier relationships with food. In one study, subjects showed improvements when it came to blood pressure, glucose regulation, and inflammation. Other studies showed that intuitive eating also led to a more positive outlook when it came to food among women and better control over blood sugar among adolescents with Type-1 diabetes.
Rawpixel.com // Shutterstock
Unfortunately, restrictive dieting has harmed many people’s views on food, negatively impacted their health, and even caused eating disorders.
Studies on intuitive eating, however, are showing that this method helps people form healthier relationships with food. In one study, subjects showed improvements when it came to blood pressure, glucose regulation, and inflammation. Other studies showed that intuitive eating also led to a more positive outlook when it came to food among women and better control over blood sugar among adolescents with Type-1 diabetes.
Canva
When it comes to discussions around health these days, the focus isn’t necessarily on going to the gym regularly and restrictive dieting. The definition of health has broadened to include more than just weight.
Instead, things, like getting enough sleep, staying hydrated, managing stress, and working through mental health issues, are starting to take center stage. This may be because traditional measures and approaches to health are found to be limiting and, in some cases, harmful. In many ways, health and wellness are linked together as it can be difficult for individuals to focus on managing their weight if they haven’t been getting enough sleep or their stress levels are high.
Canva
When it comes to discussions around health these days, the focus isn’t necessarily on going to the gym regularly and restrictive dieting. The definition of health has broadened to include more than just weight.
Instead, things, like getting enough sleep, staying hydrated, managing stress, and working through mental health issues, are starting to take center stage. This may be because traditional measures and approaches to health are found to be limiting and, in some cases, harmful. In many ways, health and wellness are linked together as it can be difficult for individuals to focus on managing their weight if they haven’t been getting enough sleep or their stress levels are high.
Bignai // Shutterstock
A person’s habits can play one of the biggest roles in improving health. However, changing habits and forming new ones can be challenging. This can be true, especially for building habits. Some people don’t like physical activity or don’t have time to work out, while others might not like healthy foods or have the money to afford them. The National Institute of Diabetes and Digestive and Kidney Diseases outlines contemplation, preparation, action, and maintenance as the four stages of forming a habit. It can take anywhere from a few weeks to a few months to form a habit.
This story originally appeared on Almond Cow and was produced and distributed in partnership with Stacker Studio.
Bignai // Shutterstock
A person’s habits can play one of the biggest roles in improving health. However, changing habits and forming new ones can be challenging. This can be true, especially for building habits. Some people don’t like physical activity or don’t have time to work out, while others might not like healthy foods or have the money to afford them. The National Institute of Diabetes and Digestive and Kidney Diseases outlines contemplation, preparation, action, and maintenance as the four stages of forming a habit. It can take anywhere from a few weeks to a few months to form a habit.
This story originally appeared on Almond Cow and was produced and distributed in partnership with Stacker Studio.
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