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Muscle Loss While Dieting to Single Digit Body Fat Levels

A question that comes up quite often is how much fat someone can lose when they are dieting down to the single digit range.  It’s often claimed that losing more than two pounds per week will cause muscle loss or that the ratio of fat to muscle lost will start to shift in a negative direction.  Even that data is usually based on studies of the obese and it is likely to change as people get leaner.  So what’s the reality.  How fast can fat be lost in lean individuals without muscle loss.

The 2 Pound Per Week Limit

The idea that weekly weight loss should be limited to 2 pounds has been bouncing around for decades although nobody seems to know where it came from.  There’s no real physiological reason for this to be a weekly maximum and much larger rates of both weight and fat loss can be achieved with extreme deficit diets.

Ignoring all of the game playing that goes on behind the scenes, Biggest Loser contestants routinely lose far more than that per week, often 10+ pounds.  Studies utilizing a protein sparing modified fast (PSMF) as per my  Rapid Fat Loss Handbook have been measured at 1/2-2/3 pounds of fat loss PER DAY.  Which is 3.5+ pounds of fat per week.  Clearly 2 lbs/week is a bogus value in a physiological sense.

So where did 2 pounds come from?  I suspect it was mostly a behavioral/reality issue.

Losing one pound of fat is usually assumed to require a 3,500 calorie deficit.  To lose even 2 pounds per week then requires a net weekly deficit of 7000 calories.  That’s 1000 calories per day.

This is a very large deficit which will require either a large amount of activity (2 hours+ for an untrained individual) or fairly large-scale calorie restriction.  Certainly this can be achieved with extreme diets but I suspect that the 2 lb/week rule came out of this idea.

For most people, a larger deficit than 1000 calories per day simply isn’t realistic.  I’d note that this was during a time when it was generally felt that more rapid fat loss was associated with poorer long-term results.  But depending on how it’s done, rapid fat loss may be superior.

Mind you, weight loss isn’t fat loss and the issue of muscle loss is a concern.  When dieting we want to improve body composition.  And initial bodyfat percentage plays a large role here: leaner individuals are more at risk for muscle loss than those carrying more bodyfat.

Rapid Weight Loss and Muscle Loss

Another issue was that analyses of the studies, always done by Gilbert Forbes, suggested that more extreme deficits caused more greater muscle loss.  But there were two major problems with this conclusion.

  1. There was no exercise, especially weight training, done.
  2. The caloric intake was stupid low.

We know that exercise spares muscle loss when dieting.  And while all types of exercise will help in total beginners, weight training is invariably found to be superior.  When most of the research on this was being done, weight training wasn’t particularly mainstream so it was never included.  If the dieters exercised it was invariably aerobic exercise.  And often no exercise was done.

And while that’s important, the second issue is probably the biggest one.  Many of the early Very Low Calorie Diet (VLCD) studies used insanely low intakes.  I am talking about things like 200-400 calories per day.  And frequently the diets were at most 50% protein.  So realistically you had people eating 100-200 calories per day of protein or 25-50 grams of protein.

Now, even those individuals with extremely high body fat percentages have some minimum protein intake requirements.  And most of these VLCD’s didn’t come close to providing it.  This is fundamentally why I set up my the Rapid Fat Loss handbook up around protein intake rather than calories.  You have to meet protein requirements on a diet or it will fail.

And when researchers finally started providing sufficient dietary protein, usually in the realm of 1.5 g/kg (0.7 g/lb) of lean body mass with a PSMF, muscle loss stopped.  It was almost as if protein was protein sparing or something.  For a 300 pound individual with 40% bodyfat, that calculates out to 122 grams of protein per day which is about 500 calories minimum. Add in some tagalong carbs and fats and you get higher calories than that.   Simply, setting calories at 300/day doesn’t allow sufficient protein.  Yet most of the data on this came from diet studies that did exactly that.

Lean vs. Obese Individuals

For what should be fairly obvious reasons, obesity researchers don’t do fat loss studies in lean individuals for the most part.  Rather, all of the research above comes from studies in the obese.  And the fact is that the system does change as people get leaner.

More work by Gilbert Forbes showed clearly that initial body fat percentage impacted on the ratio of fat and muscle mass that was lost.  On average, leaner individuals lost more than those carrying more fat.  Some early work suggested that, when you were lean, you’d lose roughly 1 pound of muscle for every 3 pounds total weight lost.  That is, up to 33% of your total weight loss might be muscle.

Many if not most aspects of physiology change as people get leaner and this is one of them.  It’s also why almost all of my book use a Category system based on bodyfat percentage for diet set up.  The reasons for the increased risk of muscle loss is multi-factorial and relates to calorie partitioning.  There are hormonal effects along with the relative difficulty of using fat versus muscle for fuel.

With the idea that faster weight loss led to more muscle loss, suggestions to limit weekly weight loss to one pound per week when you got lean were often made (other systems will use a percentage of current bodyweight based on BF%).  Dan Duchaine echoed this in the seminal Bodyopus and for a long time I suggested 1-1.5 lbs/week as the “sweet spot” for weekly weight loss for leaner individuals.   It’s still not a bad value for people on a moderate deficit.

But it’s not an absolute value.  Some can lose faster than this as people who use my Rapid Fat Loss handbook diet have shown.  True fat losses of 2-3 lbs/week in lean individuals without significant or any muscle loss is achievable for at least short periods of time in leaner individuals.  But it’s a couple of weeks tops before a break has to be taken.

But the 1-1.5 lb/week value isn’t an absolute, some can lose faster than this as lean people using my Rapid Fat Loss Handbook have shown.  True fat losses of 2-3 lbs/week in lean individuals is possible at least for short periods of time (one limitation of the RFL approach for lean people is that it should only be used for about 2 weeks straight before something less extreme is done).

So clearly it is possible to lose more than the stock-standard 1-1.5 lbs/week of true fat without muscle loss.  And understanding why and how means understanding why muscle loss tends to occur on a diet in the first place.

Why Does Muscle Loss Occur During a Diet?

There are a number of reasons that muscle loss tends to accelerate as people get leaner.  One is that the person has less bodyfat.  As fat cells shrink, it becomes more difficult to mobilize fat from them for energy.  So the body has to find something else.  That something else is usually muscle.

For that reason, protein requirements also go up as people get leaner, often reaching requirements of up to 1.5 g/lb lean body mass.  Yes, this is 1.5 g/lb lean body mass, not the 1.5 g/kg that is sufficient for the obese.

Beyond that, the big reasons are hormonal.    As people get leaner during a diet, leptin falls as does testosterone (often reaching castrate levels at the extremes of leanness).  Cortisol goes up which can hasten muscle breakdown, thyroid falls, metabolic rate falls, etc.  It’s one giant set of metabolic adaptations that the body makes to try to keep you alive.  And these factors all become more pronounced the leaner you get.

I’d note in this regard that if you look at the strategies used by professional bodybiulders, they are invariably using drugs to help offset all of the problems I’ve described.  With enough testosterone, thyroid medication, thermogenics such as clenbuterol, anti-cortisol compounds and appetite suppressants, they can show an effectively normal physiology while dieting to the extremes.

Now, these factors reverse themselves when people raise calories.  Various cyclical diets such as my own Ultimate Diet 2.0 or strategies such as The Full Diet Break can all help to normalize hormones and help to avoid all of this.   Recent research on the topic has actually finally caught up to what I was writing about in 2004 in this regard.

Training

An additional factor is that people’s ability to train intensely often goes down on a diet and maintaining the appropriate tension stimulus to keep muscle is key to avoiding muscle loss.    The entire idea of training with less intensity and more volume on a diet is asinine and only works for steroid users.  The key to avoiding muscle loss is to maintain at least some heavy training. This is what builds muscle and this is what maintains it.

But the ability to maintain training intensity in the face of a long diet at low body fat percentages is often impaired.  If the lifter can’t maintain their intensity in the gym, muscle loss is more likely.  This is yet another reason to use various cyclical dieting strategies such as refeeds or diet breaks.  By restoring muscle glycogen and raising calories, training intensity invariably improves.    This is in addition to the beneficial hormonal effects.

Dieting in the 1980’s and 1990’s

In the 1980’s and 1990’s, natural bodybuilders had all kinds of problems with muscle loss which is what led experts like Duchaine to set a 1 lb/week limit.  But the dieting practices of the time were also pretty awful.  Invariably they included:

  1. An increase in training volume with a decrease in intensity
  2. Excessive aerobic training
  3. Protein intakes of only 1 g/lb bodyweight

And when you combine those three, muscle loss is almost guaranteed. As well, nobody utilized refeeds or diet breaks.  It was just straight dieting in attempt to make it to stage.    And that just compounded a lot of the problems.

Don’t get me wrong, some people still made it work.  Why?  I can’t say.  But I would say that more had problems with the traditional approach than succeeded with it.  Many dieters probably gave up due to excessive muscle loss so what you were invariably seeing was the survivors who made it work.  And that’s misleading.

But so long as you do the opposite of those things, fat can be lost faster than 1 lb/week without muscle loss.  First, keep weight training intensity as high as you can. If you can maintain your poundages on the bar, you should.  Never cut intensity for volume and be prepared to drop volume if you need to.  Because 3 heavy sets will maintain muscle better than 6 lighter sets.

To that use cardio in a targeted manner.  Yes, some people need more than others especially as metabolism adapts down and down over the course of a diet.  If you need to do an hour per day to get lean, that’s fine.  Make sure to work up to it over the course of your diet.  But don’t do it just to do it.  Do it because you need it.

To that add sufficient protein.  For a male in the single digits, I recommend 1.5 g/lb lean body mass of protein.  Yes, this is a lot.  But that’s what is necessary.

Then strategically use refeeds and diet breaks as needed. Have one or two high calorie/higher carbohydrate days per week during the diet.  If that’s not a good approach for you, take a 7-10 day break at maintenance every 4-6 weeks.  Yes, your diet will take longer but it will work better in the long-run.

Because if you do that, you should be able to achieve a single digit body fat without muscle loss, even at fat loss rates of greater than one pound per week. With an extreme diet you might even get 2 lbs per week but you can only do it for a couple of weeks at a time.

Or if you don’t want to do that, and choose to diet in the inefficient ways that people did it 2 decades ago, you should probably stick with one pound per week to be safe.  Or, just don’t do that.

 

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