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также на сайте Берхана есть статья Intermittent Fasting and Stubborn Body Fat, где Мартин привязывает указанное им время поста к максимизации борьбы с упрямым жиром.
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Intermittent Fasting and Stubborn Body Fat
1:28 PM | Posted by Martin Berkhan
I have previously hinted that intermittent fasting sidesteps the issues associated with stubborn body fat. Indeed I rarely find any need for advanced strategies to rid my clients of stubborn body fat. I will soon tell you why, but first let me give you some background information to what I'm talking about here.
What is stubborn body fat?
Stubborn body fat refers to areas of the body that hold on to fat the longest. Generally speaking, these areas include the lower abs and lower back in men, and the lower body in women. These areas are damn hard to get lean.
How come these areas are stubborn in the first place? To understand this, let's look at how fat is mobilized (the very short version).
After you eat, insulin and fatty acids are elevated. You are in the fed state and there's zero fat burning going on. Your body is relying completely on glucose oxidation during the hours following the meal.
One way of measuring this is via the respiratory quotient (RQ). An RQ of 1.0 denotes pure carbohydrate metabolism ("storage mode"), while 0.7 denotes pure fat metabolism. To put this into perspective, consider that RQ is 0.95-1.0 for about 1.5-2 hours after a meal, 0.82-0.85 after overnight fasting and 0.72-0.8 after 16 hours of fasting.
As the hours go by and the nutrients from the meal are done being absorbed, RQ drops in conjunction with insulin. There's a shift towards fat burning and mobilization of stored fat. This process is mediated by insulin and blood-borne fatty acids; when levels drop, an energy deficit is "sensed" and catecholamines (adrenaline and nordrenaline) increase.
The catecholamines travel through the blood and bind to receptors on fat cells. A receptor can be thought of as a "lock." Hormones and neurotransmitters are keys that fit into that lock and make something happen. In this case catecholamines trigger fat mobilization by activating hormone sensitive lipase (HSL), which then shuttles the fat out of the cell to be burned off.
Now here's the critical difference between regular fat and stubborn fat: regular fat have a lot of beta-2 receptors in proportion to alpha-2 receptors.
In The Stubborn Fat Solution Lyle McDonald used the analogy of b2-receptors being "accelerators" for fat loss and a2-receptors acting as "breaks" for fat loss. That's the easiest way to think of them without getting too deep into the physiology.
The ratio between b2-receptors and a2-receptors determines how easy it is to facilitate fat loss from one region of the body. "Easy" fat has a high ratio of b2-receptors to a2-receptors, while stubborn fat has a high ratio of a2-receptors to b2-receptors.
One notorious example that Lyle brings up in his book is that women have up to nine times (!) as many a2-receptors as b2-receptors in their hip and thigh fat. Though I can't recall if similar numbers are available for lower ab and lower back fat for men, you can be sure that the a2-receptors outnumber the b2-receptors in these areas as well.
I rarely use fancy strategies for ridding my clients of stubborn body fat. They never need it. It's more or less a linear process all the way down to the shredded state.
Intermittent fasting and stubborn fat loss
How can intermittent fasting then selectively target stubborn body fat more effectively than other diets? Well, to target stubborn body fat we need to activate b2-receptors while deactivating a2-receptors. Intermittent fasting achieves this by the following mechanisms.
1. Fasting increases catecholamine levels.
2. Fasting increases abdominal subcutaneous blood flow, which means that catecholamines will have an easier time reaching those hard-to-get areas.
3. The low insulin level reached during the fast inhibits a2-receptors. A greater time spent in the low insulin state equals a greater time spent in a state where fat can be mobilized from stubborn areas. Now you're probably thinking "why not just go on a low carb diet" to keep insulin low, but keep in mind that triglycerides inhibit HSL in a similar manner as insulin.
4. My research has indicated that the ideal state of fat burning is reached after 12-18 hours of fasting. Coupled with high levels of catecholamines, increased blood flow to stubborn regions, and low insulin for a2-receptor inhibition, this time interval is the "golden age" of stubborn fat mobilization.
Let me just explain real quick what I mean by the ideal state of fat burning. Studies have examined free fatty acid (FFA) oxidation from anywhere between the overnight fasted state to three days of fasting. While FFA oxidation increases the longer time you spend in the fasted state, the contribution of fatty acids to whole body fat oxidation changes.
In short-term fasting there's a significant increase in subcutaneous FFA oxidation. That's just a fancy way of saying that you're mainly burning body fat and nothing else. For up to 14-20 hours* after a 600-calorie meal in normal-weight subjects, fat is only mobilized from body fat stores in resting individuals.
* 14-20 hours in a completely sedentary state should easily equal 12-18 hours in real life.
Past this time point, fat burning increases further. That goes without saying. But it's not necessarily the type of fat you're after that you'll be burning. Somewhere in between the 10- and 30-hour time point, the oxidation of intramuscular fat increases greatly, but no increase is seen in subcutaneous fat. Subcutaneous fat simply can't keep up with demand, so you're playing a game of diminishing returns if you push the fast too long. Coupled with the escalating rate of de novo gluconeogenesis, and subsequent risk of muscle catabolism, fasting for too long may not be very conducive for a lean individual seeking optimal lean mass retention while targeting stubborn body fat.
Men usually need to hit single-digit body fat percentage to have good abs, while women have good abdominal definition at around 15% body fat. Above is a picture of natural body fitness champ and intermittent fasting afficionado Kristine Weber.
Science vs real life
One obvious question critically inclined readers should ask themselves is whether special strategies to mobilize stubborn fat is even needed in the first place. After all, people have gotten ripped without intermittent fasting or the strategies laid out in The Stubborn Fat Solution by Lyle McDonald. Is it not just a question of dropping low enough in body fat percentage?
If we compare a traditional calorie deficit of 3500 kcal per week on a conservative diet vs 3500 kcal on an intermittent fasting setup (or with The Stubborn Fat Solution), would there be any difference in regional fat loss assuming all other factors were kept constant? I don't think we'll ever know, so this boils down to relying on theory and practical experience.
My personal experience is that intermittent fasting helps with stubborn fat loss compared to a conservative diet. This little anecdote is obviously riddled with confounders, and maybe even wishful thinking, but if you take a look at some pictures from my younger days (and here), you'll see that I was quite lean during the modelling days. However, I still had some fat covering the lower ab region and never really seemed to lean out well no matter how hard I tried. Sure, I would lose weight when I cut calories, but not from the right areas. I always ended up getting extremely lean legs, arms and shoulders. I also lost a lot of muscle in my desperate attempts to get good abs, but that might just boil down to me dieting like a retard. As you can see in some more recent pics, I don't have those types of problems any more.
Adding to this anecdotal evidence of mine, I have heard similar feedback from clients and blog readers. Intermittent fasting seems very conducive for targeting stubborn body fat. Got a similar experience to report? Let me know.
1:28 PM | Posted by Martin Berkhan
I have previously hinted that intermittent fasting sidesteps the issues associated with stubborn body fat. Indeed I rarely find any need for advanced strategies to rid my clients of stubborn body fat. I will soon tell you why, but first let me give you some background information to what I'm talking about here.
What is stubborn body fat?
Stubborn body fat refers to areas of the body that hold on to fat the longest. Generally speaking, these areas include the lower abs and lower back in men, and the lower body in women. These areas are damn hard to get lean.
How come these areas are stubborn in the first place? To understand this, let's look at how fat is mobilized (the very short version).
After you eat, insulin and fatty acids are elevated. You are in the fed state and there's zero fat burning going on. Your body is relying completely on glucose oxidation during the hours following the meal.
One way of measuring this is via the respiratory quotient (RQ). An RQ of 1.0 denotes pure carbohydrate metabolism ("storage mode"), while 0.7 denotes pure fat metabolism. To put this into perspective, consider that RQ is 0.95-1.0 for about 1.5-2 hours after a meal, 0.82-0.85 after overnight fasting and 0.72-0.8 after 16 hours of fasting.
As the hours go by and the nutrients from the meal are done being absorbed, RQ drops in conjunction with insulin. There's a shift towards fat burning and mobilization of stored fat. This process is mediated by insulin and blood-borne fatty acids; when levels drop, an energy deficit is "sensed" and catecholamines (adrenaline and nordrenaline) increase.
The catecholamines travel through the blood and bind to receptors on fat cells. A receptor can be thought of as a "lock." Hormones and neurotransmitters are keys that fit into that lock and make something happen. In this case catecholamines trigger fat mobilization by activating hormone sensitive lipase (HSL), which then shuttles the fat out of the cell to be burned off.
Now here's the critical difference between regular fat and stubborn fat: regular fat have a lot of beta-2 receptors in proportion to alpha-2 receptors.
In The Stubborn Fat Solution Lyle McDonald used the analogy of b2-receptors being "accelerators" for fat loss and a2-receptors acting as "breaks" for fat loss. That's the easiest way to think of them without getting too deep into the physiology.
The ratio between b2-receptors and a2-receptors determines how easy it is to facilitate fat loss from one region of the body. "Easy" fat has a high ratio of b2-receptors to a2-receptors, while stubborn fat has a high ratio of a2-receptors to b2-receptors.
One notorious example that Lyle brings up in his book is that women have up to nine times (!) as many a2-receptors as b2-receptors in their hip and thigh fat. Though I can't recall if similar numbers are available for lower ab and lower back fat for men, you can be sure that the a2-receptors outnumber the b2-receptors in these areas as well.
I rarely use fancy strategies for ridding my clients of stubborn body fat. They never need it. It's more or less a linear process all the way down to the shredded state.
Intermittent fasting and stubborn fat loss
How can intermittent fasting then selectively target stubborn body fat more effectively than other diets? Well, to target stubborn body fat we need to activate b2-receptors while deactivating a2-receptors. Intermittent fasting achieves this by the following mechanisms.
1. Fasting increases catecholamine levels.
2. Fasting increases abdominal subcutaneous blood flow, which means that catecholamines will have an easier time reaching those hard-to-get areas.
3. The low insulin level reached during the fast inhibits a2-receptors. A greater time spent in the low insulin state equals a greater time spent in a state where fat can be mobilized from stubborn areas. Now you're probably thinking "why not just go on a low carb diet" to keep insulin low, but keep in mind that triglycerides inhibit HSL in a similar manner as insulin.
4. My research has indicated that the ideal state of fat burning is reached after 12-18 hours of fasting. Coupled with high levels of catecholamines, increased blood flow to stubborn regions, and low insulin for a2-receptor inhibition, this time interval is the "golden age" of stubborn fat mobilization.
Let me just explain real quick what I mean by the ideal state of fat burning. Studies have examined free fatty acid (FFA) oxidation from anywhere between the overnight fasted state to three days of fasting. While FFA oxidation increases the longer time you spend in the fasted state, the contribution of fatty acids to whole body fat oxidation changes.
In short-term fasting there's a significant increase in subcutaneous FFA oxidation. That's just a fancy way of saying that you're mainly burning body fat and nothing else. For up to 14-20 hours* after a 600-calorie meal in normal-weight subjects, fat is only mobilized from body fat stores in resting individuals.
* 14-20 hours in a completely sedentary state should easily equal 12-18 hours in real life.
Past this time point, fat burning increases further. That goes without saying. But it's not necessarily the type of fat you're after that you'll be burning. Somewhere in between the 10- and 30-hour time point, the oxidation of intramuscular fat increases greatly, but no increase is seen in subcutaneous fat. Subcutaneous fat simply can't keep up with demand, so you're playing a game of diminishing returns if you push the fast too long. Coupled with the escalating rate of de novo gluconeogenesis, and subsequent risk of muscle catabolism, fasting for too long may not be very conducive for a lean individual seeking optimal lean mass retention while targeting stubborn body fat.
Men usually need to hit single-digit body fat percentage to have good abs, while women have good abdominal definition at around 15% body fat. Above is a picture of natural body fitness champ and intermittent fasting afficionado Kristine Weber.
Science vs real life
One obvious question critically inclined readers should ask themselves is whether special strategies to mobilize stubborn fat is even needed in the first place. After all, people have gotten ripped without intermittent fasting or the strategies laid out in The Stubborn Fat Solution by Lyle McDonald. Is it not just a question of dropping low enough in body fat percentage?
If we compare a traditional calorie deficit of 3500 kcal per week on a conservative diet vs 3500 kcal on an intermittent fasting setup (or with The Stubborn Fat Solution), would there be any difference in regional fat loss assuming all other factors were kept constant? I don't think we'll ever know, so this boils down to relying on theory and practical experience.
My personal experience is that intermittent fasting helps with stubborn fat loss compared to a conservative diet. This little anecdote is obviously riddled with confounders, and maybe even wishful thinking, but if you take a look at some pictures from my younger days (and here), you'll see that I was quite lean during the modelling days. However, I still had some fat covering the lower ab region and never really seemed to lean out well no matter how hard I tried. Sure, I would lose weight when I cut calories, but not from the right areas. I always ended up getting extremely lean legs, arms and shoulders. I also lost a lot of muscle in my desperate attempts to get good abs, but that might just boil down to me dieting like a retard. As you can see in some more recent pics, I don't have those types of problems any more.
Adding to this anecdotal evidence of mine, I have heard similar feedback from clients and blog readers. Intermittent fasting seems very conducive for targeting stubborn body fat. Got a similar experience to report? Let me know.
Сообщение изменено: Znatok Ne (23 июля 2013 - 11:16)
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