Thanks for asking. I'll first explain the process (because I want to highlight why IF matters), and then I'll answer your question directly. It's going to take a little bit to properly elaborate, but I believe it's worth your time to read.
We first need to choose which of the following macronutrients contribute most to weight gain: protein, fat, or carbohydrates. Proteins (or, rather, amino acids) are not known for contributing to body fat in any significant manner. Fat was once thought to be the main contributor when calories--not carbohydrates--became accepted as fattening. However, modern science shows fat has little significant contribution to body fat and that the real contributor to body fat are carbohydrates. The discovery of leptin about 30 years ago finally shows why.
Carbs are sugars. Sugars, such as glucose, are the main source of fuel in the body, as they are eventually synthesized into ATP. Blood glucose levels are regulated by the hormone insulin. Elevated blood glucose levels increases insulin production, whereas low blood glucose decreases insulin production (with glucagon helping stabilize blood glucose levels). High insulin levels promotes anabolism, whereas low insulin levels promotes catabolism. Creating body fat is an anabolic process, whereas burning body fat is a catabolic process. Putting it all together, eating carbs inhibits the essential catabolic processes for burning fat.
While entirely cutting out carbs should be the answer, it's not. Many obese people report failure to lose weight on ketogenic diets. Why? The hormone leptin. See, leptin levels increase with insulin levels. Leptin signals the availability of energy reserves in the body. Adipose tissue (that is, body fat) is the primary producer of leptin. Importantly, leptin levels vary exponentially with body fat. The obese individual's body is so oversaturated with leptin, the body becomes resistant to leptin.
Decreased leptin levels will cause body fat to be burned. On a ketogenic diet, catabolic processes initially cause a reduction in body fat, which then decreases leptin production. Because the obese body has leptin resistance, the leptin production decrease is interpreted by the brain as a severe drop in available energy reserves, causing total energy expenditure to be immediately reduced and placing the body in "starvation mode." At this point, eliminating body fat actually becomes more difficult, as excess carbs become anabolized into body fat due to decreased energy expenditures.
So, to finally get to your question, how do carbs matter with respect to leptin? To lose weight over months and years, an obese person needs to eat carbs to (1) keep their leptin levels stable over the course of each week to prevent the body from entering starvation mode while (2) maximizing the efficacy of catabolic processes. As the body gradually recovers from its leptin resistance (which will likely take time), the body will shed fat without triggering the energy-minimization mode.
In this paradigm, your total energy expenditure determines how fast fat will be burned. According to the book "The Obesity Code", "total energy expenditure is the sum of basal metabolic rate, thermogenic effect of food, nonexercise activity thermogenesis, excess post-exercise oxygen consumption [(EPOC),] and exercise". Of these five factors, EPOC is mostly likely underutilized. A simple 10-minute HIIT routine every other day will regularly drive EPOC, which causes ATP synthesis. When an person isn't eating carbs, the body dips into fat stores to acquire the necessary glucose for ATP synthesis. Note that with this approach, exercise isn't strictly necessary but becomes extremely beneficial to maximize the efficacy of catabolic processes.
Intermittent fasting should work as long as the specific protocol doesn't decrease leptin levels such that the obese body enters starvation mode. In my opinion, the most workable approach for people is to try their best to completely eliminate carbs Monday-Friday, eat all the carbs they want on the weekends, and do the bare minimum of a 10-minutes HIIT routine every other day.
> Intermittent fasting should work as long as the specific protocol doesn't decrease leptin levels such that the obese body enters starvation mode. In my opinion, the most workable approach for people is to try their best to completely eliminate carbs Monday-Friday, eat all the carbs they want on the weekends, and do the bare minimum of a 10-minutes HIIT routine every other day.
This is just calorie cycling with extra steps.
It doesn't honestly matter if it is 5 days on, 2 days off, or 2 months on, 2 weeks off. It is up to a person's individual biology. When the scale stops moving, up calorie intake to the extent that the scale doesn't move up more than a smidge, wait a bit, then drop calories again.
TKD, CKD, intermittent fasting, dirty keto, keto with a once a month weekend pizza binge, whatever, almost any combo of "eat less for awhile, then eat normal for little bit, then eat less again".
That's almost right, but it's carb cycling, not calorie cycling. The difference does matter.
>TKD, CKD, intermittent fasting, dirty keto, keto with a once a month weekend pizza binge, whatever, almost any combo of "eat less for awhile, then eat normal for little bit, then eat less again".
I believe that the best approaches, for a given period, will be 2/3 of the time on minimal-to-no carbs, then 1/3 on carbs (which, for seven days, rounds to 5-off / 2-on). The leptin information also suggests that an obese person shouldn't be off carbs for long periods of time, and one week is a nice time frame for people (go low-carb during the work week, have carbs on the weekend).
We first need to choose which of the following macronutrients contribute most to weight gain: protein, fat, or carbohydrates. Proteins (or, rather, amino acids) are not known for contributing to body fat in any significant manner. Fat was once thought to be the main contributor when calories--not carbohydrates--became accepted as fattening. However, modern science shows fat has little significant contribution to body fat and that the real contributor to body fat are carbohydrates. The discovery of leptin about 30 years ago finally shows why.
Carbs are sugars. Sugars, such as glucose, are the main source of fuel in the body, as they are eventually synthesized into ATP. Blood glucose levels are regulated by the hormone insulin. Elevated blood glucose levels increases insulin production, whereas low blood glucose decreases insulin production (with glucagon helping stabilize blood glucose levels). High insulin levels promotes anabolism, whereas low insulin levels promotes catabolism. Creating body fat is an anabolic process, whereas burning body fat is a catabolic process. Putting it all together, eating carbs inhibits the essential catabolic processes for burning fat.
While entirely cutting out carbs should be the answer, it's not. Many obese people report failure to lose weight on ketogenic diets. Why? The hormone leptin. See, leptin levels increase with insulin levels. Leptin signals the availability of energy reserves in the body. Adipose tissue (that is, body fat) is the primary producer of leptin. Importantly, leptin levels vary exponentially with body fat. The obese individual's body is so oversaturated with leptin, the body becomes resistant to leptin.
Decreased leptin levels will cause body fat to be burned. On a ketogenic diet, catabolic processes initially cause a reduction in body fat, which then decreases leptin production. Because the obese body has leptin resistance, the leptin production decrease is interpreted by the brain as a severe drop in available energy reserves, causing total energy expenditure to be immediately reduced and placing the body in "starvation mode." At this point, eliminating body fat actually becomes more difficult, as excess carbs become anabolized into body fat due to decreased energy expenditures.
So, to finally get to your question, how do carbs matter with respect to leptin? To lose weight over months and years, an obese person needs to eat carbs to (1) keep their leptin levels stable over the course of each week to prevent the body from entering starvation mode while (2) maximizing the efficacy of catabolic processes. As the body gradually recovers from its leptin resistance (which will likely take time), the body will shed fat without triggering the energy-minimization mode.
In this paradigm, your total energy expenditure determines how fast fat will be burned. According to the book "The Obesity Code", "total energy expenditure is the sum of basal metabolic rate, thermogenic effect of food, nonexercise activity thermogenesis, excess post-exercise oxygen consumption [(EPOC),] and exercise". Of these five factors, EPOC is mostly likely underutilized. A simple 10-minute HIIT routine every other day will regularly drive EPOC, which causes ATP synthesis. When an person isn't eating carbs, the body dips into fat stores to acquire the necessary glucose for ATP synthesis. Note that with this approach, exercise isn't strictly necessary but becomes extremely beneficial to maximize the efficacy of catabolic processes.
Intermittent fasting should work as long as the specific protocol doesn't decrease leptin levels such that the obese body enters starvation mode. In my opinion, the most workable approach for people is to try their best to completely eliminate carbs Monday-Friday, eat all the carbs they want on the weekends, and do the bare minimum of a 10-minutes HIIT routine every other day.