Journal Review #5: Weight Loss from Intermittent Fasting is Equivalent to Constant Caloric Restriction
August 19, 2022
Background Information - Obesity is a silent pandemic that is invading millions of homes worldwide, and while knowledge on the subject is increasing, the vast majority of treatments and preventives available to the general public are extremely ineffective. It is well-known in the scientific community that obesity is positively correlated with insulin resistance; that is, obese subjects are likely to have greater insulin resistance than nonobese (lean) subjects. Insulin resistance is extremely problematic for metabolic health. Insulin is a hormone released from the pancreas when carbohydrates, and to a lesser degree, fats, enter the bloodstream. This hormone can bind to the insulin receptor found in nearly all cells, but mostly in adipocytes and skeletal muscle cells due to their active role in metabolism. When insulin binds to its receptor, the main effect is to insert a glucose transport protein into the cell membrane. This glucose transport protein (GLUT) allows glucose from the blood to enter the cell and be used for fuel. However, in obesity or type 2 diabetes mellitus, when insulin resistance is high, insulin is unable to efficiently cause a cascade of events in the target cell. Because the insulin cannot cause a signal cascade in the cell, no GLUT protein is inserted, and glucose cannot enter the target cell, so blood glucose remains heightened.
As a result of insulin resistance, blood glucose remains high, thus altering blood viscosity. As well as influencing blood viscocity, high blood glucose impacts kidney health in a negative manner and forces the beta cells of the islets of Langerhans located in the pancreas to produce more insulin. The increase in insulin production is a compensatory mechanism for insulin resistance, and in doing so, damage accumulates in the insulin-producing cells. Thus over time, insulin release rapidly declines and causes a spike in blood glucose, which exasperates symptoms of hyperglycemia. Chronic hyperglycemia is correlated with Alzheimer’s disease, cardiovascular disease, retinopathy, neuropathy, and so much more. Although insulin resistance is not the only metabolic problem associated with obesity, it is responsible for a large cascade of events, making it an extremely important parameter when assessing metabolic health.
Over the last few years, the term "fasting" has seen the best and worst of social media. While fasting has become somewhat of a buzzword recently due to the misinformation surrounding its pros and cons, it still has scientifically-driven benefits. Fasting is known to induce ketosis, which is the burning of fat for fuel, which acts to essentially reset glucose regulation mechanisms. This severe caloric depletion allows the body to regulate glucose, lose excess fat, and increase ketone bodies, which may have a beneficial role in regulating metabolism acutely. The aim of this journal review is to bring awareness to the benefits of fasting on metabolic health.
It has been shown that weight loss can drastically improve metabolic issues associated with obesity. A new issue that arises is adherence to a nutritional program that restricts energy intake. In order for a subject to lose fat, they must expend more energy than they are taking in from food. To track this energy, the most common unit of energy is a calorie, but the general public is misinformed about what exactly a calorie is. Like a calorie, a joule is a unit of energy. In fact, one joule is the amount of work required to produce one watt of power for one second, where work is energy and it is equivalent to the amount of force times the displacement (distance). One joule is actually equivalent to 0.239 calories. Therefore, 0.239 calories is the amount of work required to produce one watt of power for one second. The nutrition label on our foods is actually written as "Calories" or "kcals", and this just means one thousand calories, just like one "kg" is one thousand grams. The foods we eat provide us with energy, and we use this energy by breaking apart the molecules within the food to assist in the production of ATP. The simplest example would be glycolysis. Our bodies can absorb glucose into the bloodstream. Once the glucose is in the bloodstream, it can pass through a GLUT protein and into a cell, such as a skeletal muscle cell. This cell, with the help of enzymes, breaks down the glucose molecules into two pyruvate molecules, and as a byproduct, ATP is produced. The pyruvate molecules can then go onto the Kreb’s cycle to fuel the electron transport chain, which ends in the production of ATP via a proton gradient in the mitochondria. In general, it is taught that one glucose molecule through this pathway yields 38 ATP. Taken altogether, the general public has a misconceived notion of the calorie, and understanding that a calorie is a unit of energy helps illustrate the connection between energy expenditure and energy intake.
A major problem with losing weight is dieting. This is due to many factors and feedback loops that will be discussed in a later paper. One of the many problems that come with dieting is that the subject is energy restricted. The intake of energy, measured in calories, is less than the expenditure of energy, which can also be measured in calories. There are many pathways in the body that can sense nutrients and energy. One of them is the AMP-activated protein kinase (AMPK) pathway. The AMPK pathway leads to many cellular changes, including downregulation of mammalian target of rapamycin (mTOR), the main anabolic/growth pathway. Shutting down mTOR can lead to changes in glucose metabolism and, in combination with AMPK’s effects on increasing glycolysis, can lower blood glucose, thus making the subject feel extremely hungry.
Brief Journal Review - One solution to resolve poor diet adherence is intermittent fasting. The psychological effects of eating in a small time frame are more promising/managable than continual hunger. This current study investigates whether intermittent fasting for two days followed by five days of normal eating would yield the same benefits as constant caloric restriction. For this study, 63 overweight or obese adults with diagnosed type 2 diabetes mellitus were randomly assigned to either constant energy restriction or intermittent energy restriction. Due to undisclosed information, 24 subjects dropped out of the trial, leaving 26 subjects in the intermittent group and 25 subjects in the constant group.
A registered dietitian was included in the study to provide dietary information to all of the subjects equally. This article does a solid job of portraying the kind of education the patients received, including mentioning that recipe ideas were included in the education. The trial lasted for 12 weeks and each measurement upon appointment was performed after the subject had overnight fasted.
This study is a systematic review, similar to the umbrella review mentioned in a previous article. A systematic review is a review of trials. In this case, the author includes randomized controlled trials consisting of adults implementing intermittent fasting. The systematic review is comprised of four trials and a single case report. Therefore, more randomized controlled trials should be conducted to increase the statistical power of these reviews.
The randomized controlled trials were selected and consisted of overweight or obese subjects with a diagnosis of type 2 diabetes who were taking prescribed anti-diabetic agents. All trials measured changes in body weight, hemoglobin A1C, and fasting blood glucose. The review states that intermittent fasting is effective at decreasing all of the previously mentioned measurements. The main takeaway from this study is that constantly being energy restricted is not significantly better for diabetes or weight loss than being intermittently energy restricted. The importance of intermittent energy restriction is that adherence to an energy restriction may be higher compared to a constant energy restricted state.
Takeaways - As many professionals say, "the best _____ is the _____ you can stick to". There is absolute truth in this phrase because adhering to a system of habits is more beneficial than having peaks and valleys of varying behavior. An example of this is dieting. If a person eats 3x a day, that is 21 meals a week, and if that person eats according to their diet plan for 60% of those meals, then they are only eating 13 good meals a week. That is still 8 meals that are detrimental to their health and can vary from person to person. One person may eat 1 or 2 scoops of ice cream and that's a bad meal for them, but another person can eat a whole tub of ice cream and they equate that to one bad meal. Depending on where the individual falls on this spectrum, diet adherence is proportionally important for the health benefits associated with the particular diet.
As a result of insulin resistance, blood glucose remains high, thus altering blood viscosity. As well as influencing blood viscocity, high blood glucose impacts kidney health in a negative manner and forces the beta cells of the islets of Langerhans located in the pancreas to produce more insulin. The increase in insulin production is a compensatory mechanism for insulin resistance, and in doing so, damage accumulates in the insulin-producing cells. Thus over time, insulin release rapidly declines and causes a spike in blood glucose, which exasperates symptoms of hyperglycemia. Chronic hyperglycemia is correlated with Alzheimer’s disease, cardiovascular disease, retinopathy, neuropathy, and so much more. Although insulin resistance is not the only metabolic problem associated with obesity, it is responsible for a large cascade of events, making it an extremely important parameter when assessing metabolic health.
Over the last few years, the term "fasting" has seen the best and worst of social media. While fasting has become somewhat of a buzzword recently due to the misinformation surrounding its pros and cons, it still has scientifically-driven benefits. Fasting is known to induce ketosis, which is the burning of fat for fuel, which acts to essentially reset glucose regulation mechanisms. This severe caloric depletion allows the body to regulate glucose, lose excess fat, and increase ketone bodies, which may have a beneficial role in regulating metabolism acutely. The aim of this journal review is to bring awareness to the benefits of fasting on metabolic health.
It has been shown that weight loss can drastically improve metabolic issues associated with obesity. A new issue that arises is adherence to a nutritional program that restricts energy intake. In order for a subject to lose fat, they must expend more energy than they are taking in from food. To track this energy, the most common unit of energy is a calorie, but the general public is misinformed about what exactly a calorie is. Like a calorie, a joule is a unit of energy. In fact, one joule is the amount of work required to produce one watt of power for one second, where work is energy and it is equivalent to the amount of force times the displacement (distance). One joule is actually equivalent to 0.239 calories. Therefore, 0.239 calories is the amount of work required to produce one watt of power for one second. The nutrition label on our foods is actually written as "Calories" or "kcals", and this just means one thousand calories, just like one "kg" is one thousand grams. The foods we eat provide us with energy, and we use this energy by breaking apart the molecules within the food to assist in the production of ATP. The simplest example would be glycolysis. Our bodies can absorb glucose into the bloodstream. Once the glucose is in the bloodstream, it can pass through a GLUT protein and into a cell, such as a skeletal muscle cell. This cell, with the help of enzymes, breaks down the glucose molecules into two pyruvate molecules, and as a byproduct, ATP is produced. The pyruvate molecules can then go onto the Kreb’s cycle to fuel the electron transport chain, which ends in the production of ATP via a proton gradient in the mitochondria. In general, it is taught that one glucose molecule through this pathway yields 38 ATP. Taken altogether, the general public has a misconceived notion of the calorie, and understanding that a calorie is a unit of energy helps illustrate the connection between energy expenditure and energy intake.
A major problem with losing weight is dieting. This is due to many factors and feedback loops that will be discussed in a later paper. One of the many problems that come with dieting is that the subject is energy restricted. The intake of energy, measured in calories, is less than the expenditure of energy, which can also be measured in calories. There are many pathways in the body that can sense nutrients and energy. One of them is the AMP-activated protein kinase (AMPK) pathway. The AMPK pathway leads to many cellular changes, including downregulation of mammalian target of rapamycin (mTOR), the main anabolic/growth pathway. Shutting down mTOR can lead to changes in glucose metabolism and, in combination with AMPK’s effects on increasing glycolysis, can lower blood glucose, thus making the subject feel extremely hungry.
Brief Journal Review - One solution to resolve poor diet adherence is intermittent fasting. The psychological effects of eating in a small time frame are more promising/managable than continual hunger. This current study investigates whether intermittent fasting for two days followed by five days of normal eating would yield the same benefits as constant caloric restriction. For this study, 63 overweight or obese adults with diagnosed type 2 diabetes mellitus were randomly assigned to either constant energy restriction or intermittent energy restriction. Due to undisclosed information, 24 subjects dropped out of the trial, leaving 26 subjects in the intermittent group and 25 subjects in the constant group.
A registered dietitian was included in the study to provide dietary information to all of the subjects equally. This article does a solid job of portraying the kind of education the patients received, including mentioning that recipe ideas were included in the education. The trial lasted for 12 weeks and each measurement upon appointment was performed after the subject had overnight fasted.
This study is a systematic review, similar to the umbrella review mentioned in a previous article. A systematic review is a review of trials. In this case, the author includes randomized controlled trials consisting of adults implementing intermittent fasting. The systematic review is comprised of four trials and a single case report. Therefore, more randomized controlled trials should be conducted to increase the statistical power of these reviews.
The randomized controlled trials were selected and consisted of overweight or obese subjects with a diagnosis of type 2 diabetes who were taking prescribed anti-diabetic agents. All trials measured changes in body weight, hemoglobin A1C, and fasting blood glucose. The review states that intermittent fasting is effective at decreasing all of the previously mentioned measurements. The main takeaway from this study is that constantly being energy restricted is not significantly better for diabetes or weight loss than being intermittently energy restricted. The importance of intermittent energy restriction is that adherence to an energy restriction may be higher compared to a constant energy restricted state.
Takeaways - As many professionals say, "the best _____ is the _____ you can stick to". There is absolute truth in this phrase because adhering to a system of habits is more beneficial than having peaks and valleys of varying behavior. An example of this is dieting. If a person eats 3x a day, that is 21 meals a week, and if that person eats according to their diet plan for 60% of those meals, then they are only eating 13 good meals a week. That is still 8 meals that are detrimental to their health and can vary from person to person. One person may eat 1 or 2 scoops of ice cream and that's a bad meal for them, but another person can eat a whole tub of ice cream and they equate that to one bad meal. Depending on where the individual falls on this spectrum, diet adherence is proportionally important for the health benefits associated with the particular diet.
Meet The Author
Hello everyone,
My name is Joshua Giblin. I am a post-bachelor researcher/research technician at USC. My interests range from nutrition to nanomedicine and also practical science to improve everyday life. Through this blog, I aim to communicate practical scientific research and present it to curious individuals so that an educated decision can be made. Thank you for reading the blog and showing your support.
Editors
A special thanks to the people involved behind the scenes. Without them, these informative and influential posts would not be what they are.
Anna Richardson - Undergraduate
Molly Giblin - High School Student
