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4 Reasons to Change Body Composition

While I’ve written numerous articles on the topic of body composition I should probably address a more fundamental question which is this: why do people want to change body composition at all?   That is, what reasons (good or bad) might people have for wanting to gain (or even lose) muscle or lose (or even gain) fat.    As there are four potential goals that someone might have, there will be four potential reasons for them to change body composition.

Reason 1: Why Lose Fat?

At any given time, some ludicrous percentage of the population is trying to lose weight and/or fat.  If you’re not clear on the distinction, I’d point you to my article on what body composition means.    As so often is the case, context is key and different populations usually have different reasons for seeking this goal.

Bodybuilders and Physique Athletes

It’s probably safe to say that bodybuilders and other physique athletes are the ones who are at least the most visible in terms of their extreme levels of fat loss.  They are often the most successful as well.  While their goals are often also vanity driven, the simple fact is that reducing body fat to an appropriate level is required for competition purposes.  In the case of bodybuilding, this can often reducing body fat to what are unhealthy levels.

A male may reach 3-4% body fat on competition day, females have been measured in the single digits as well although few will maintain those levels for very long. This does some nasty things to hormones and women can do real damage to their health if they try to maintain that level for extended periods. As noted, most don’t but some try.

Certainly, figure and fitness has become more relaxed in recent years with higher body fat levels and “softer” looks being the goal.  But fat loss is usually a primary goal for these types of individuals (it’s not a stretch to say that they are professional dieters) as part of their overall competition goals.

Even bodybuilders with no interest in stepping on stage typically wants to keep their body fat levels low enough to have some definition and “be buff”.  While this requires gaining some amount of muscle mass, it usually mandates eventually losing some fat as well.

Female physique types, who are usually less interested in massive muscles in the first place (there are exceptions, females who want to be massive and/or beastly strong) and tend to be more concerned about overall appearance.  Generally speaking this means lean hips and thighs although this is usually the last place for women to lose fat.

Performance Athletes

Performance athletes frequently want to drop fat (or sometimes just weight) to either improve performance or simply make it into a specific weight class.  Clearly, in some cases, losing fat and/or weight helps performance by increasing the strength/power to weight ratio. Endurance athletes tend to benefit from being lighter because the less mass they have to move against gravity, the faster they go.  There are occasional exceptions (heavyweight rowers come to mind).

However, taken to extremes, dropping too much weight or fat can cause performance to plummet.  Whether this is due to the reduced weight/fat per se or simply the effort (excessive + dietary restriction) required to make it happen is difficult to determine and probably both contribute.

For sports performance, there is usually an optimal level of bodyfat but optimal isn’t the same as minimal.  Many athletes get confused about the distinction.

The General Public

Of course, not everyone wants to lose fat for athletic, performance or bodybuilding reasons.  While many will pay at least lip service to the idea of losing weight or fat for health reasons, let’s face up to the facts: the grand majority of people who pursue fat loss do it for vanity driven reasons.  Put bluntly: they want to look better naked.   I’m not saying this is a bad goal.  Let’s just call it what it is.

Related to this, some people tie in their sense of self-confidence with their physique; when they’re lean they’re confident, when they’re not, they’re not. Others are doing it to meet some societally driven idea of “perfection” or “beauty”.  I’ll leave argument over that to the sociologists.

It’s worth mentioning that while this used to apply primarily to women, there are an increasing number of men showing issues with eating disorders and other unhealthy eating and training habits (including a massive increase in elective plastic surgery for men).  At one point it was thought that eating disorders only occurred in men but this is clearly not the case.  Both anorexia and bulimia are potentially fatal.

Of course, some individuals want, have to or need to lose fat/weight for health reasons.  High blood cholesterol, high blood pressure, Syndrome X (aka Type II diabetes), arthritis, etc. are all often positively impacted by even moderate amounts of weight loss.  Research suggests that as little as a 10% weight loss (e.g. 20 lbs for a 200 lb person, 30 lbs for a 300 lb person) can drastically improve health parameters.

Reason 2: Why Gain Fat?

It may seem strange to think that some individuals actively want to gain fat but this is not as uncommon a goal as many thing.     It’s interesting to note that in some cultures, fatness is not the social negative that it tends to be in the Western world.

Women are frequently moved into fattening tents prior to marriage, and one culture even has a ritual fattening period that signals a boy’s growth into a man.  I’d note that there’s no real trick to this: they accomplish this fattening by making the victims eat a lot and sit on their butts all day.

It’s probably fair to say that in most Western cultures, it’d be a little unusual for someone to specifically want to gain fat. But there are always exceptions.


For some athletes (especially female) increasing bodyfat may actually be healthier for them in the long-term.    Studies show that women’s hormones (and men’s for the record) can be severely disrupted under certain conditions (usually the combination of a low body fat and excessive caloric restriction) and this can cause bone loss and other problems at a very early age.  Studies of female gymnasts have found bone densities similar to that seen in severe osteoporosis in old women.  This is not a good thing.

After physique contests, both female and male athletes should/must regain body fat to have any chance of ever normalizing their hormone levels, health or performance.    This is simply the physiological reality.

For other performance athletes, many find that they stay healthier by maintaining higher body fat percentage in their off-season while they are training before reducing it again for their competition season.  In The Women’s Book I described a case-study of a female runner who did exactly that.  She’d compete at the lower extreme of BF% while increasing it so that she could train effectively.

For other athletes, such as a football lineman or a sumo wrestler, the quality of weight gained may not be as critical as just being a walking human wall.  Carrying extra fat may actually be beneficial since it can provide some protection against the other large men who are going to be running into you at high speeds with violence on their mind.  Other athletes, usually those who tried to get too lean often find that they perform better at a slightly higher BF%.

Of course, gaining fat for the sake of gaining fat is almost always a poor idea health-wise (and there has been an alarming increase in death at a young age among athletes in sports where the body weight requirements keep going up and up and up), unless someone was unhealthily lean in the first place.

But sports performance and optimal health aren’t always compatible.  If being 350-400 lbs (with 40% body fat) is required to be a pro football lineman and make the big bucks, so be it.  I’d note that taking the fat off after they retire is often a real problem for these types of athletes.  They tend to be so used to eating everything in sight that the idea of not doing so is a very rough change to make.


Finally, sometimes non-athletic individuals need to gain weight or fat as well. Although relatively more rare, some individuals are unhealthily underweight or underfat. I’m not talking about the anorexic eating disorder types (who need to be medically supervised during their weight gain) but folks who simply can’t seem to gain enough weight to be healthy, energetic and vigorous.  This tends to be a small percentage of the population but anybody who reads this site regularly knows that I’m all about completeness.

Reason 3: Why Gain Muscle?

The same individuals who typically want to reduce fat for either cosmetic or performance reasons frequently want to gain muscle mass for the very same reasons.

Physique Athletes

Bodybuilders may need (or simply want) to gain muscle mass to improve their size and overall shape. This may be overall size increases or just increases in specific muscle groups for reasons of symmetry and balance.

As I mentioned above, serious trainees with no intention of ever competing often want to gain muscle.  Men usually want to “Be buff” while women want to “get toned”.  Both simply mean having sufficient muscle mass at a low enough body fat.  Even there some women and men just want to be muscular as hell even if they have no intention of competing.

Performance Athletes

Performance athletes may find that performance increases with more muscle and strength although how much of each depends strongly on the type of sport.  Many athletes (e.g. sprinters) have to balance out the requirement for strength and power with carrying too much body weight.  It is often a fine balance.  Other sports aren’t quite as demanding for that balance and if more muscle mass leads to more strength and power, performance often goes up.

For some athletes (especially endurance), too much muscle mass is a hindrance and will slow them down beyond a certain point.  Heavyweight rowers tend to be an odd exception since their weight is supported by the boat.  As with body fat, optimal levels of muscle mass, enough for efficient performance, but not so much that it slows the athlete down is the goal for these athletes.

There are also athletes who can’t gain too much muscle because of aesthetic requirements of their sport (i.e. gymnastics and figure skating).

The General Public

Even the general public is often interested in some amount of muscle mass gain in this day and age.  Like fat loss, most of this tends to be driven by cosmetic reasons. Males want to ‘be buff’ and females are finding that even small amounts of muscle mass drastically improve their appearance.

Of course, there can also be health benefits to gaining muscle mass.  Massive amounts of research is focusing on the muscle loss (called sarcopenia) that can occur with aging and finding ways to improve muscle mass (usually through training and nutritional intervention) in an increasingly aging population is key is important for both health and functional reasons (e.g. being able to carry your own groceries or get up out a chair without help).

Of course, in extreme situations such as wasting (cancer, AIDS, etc.) maintaining muscle mass is of equal health importance.  As it turns out, the loss of too much muscle mass will cause death and finding ways to slow or stop the loss of muscle that occurs is of huge importance.

Reason 4: Why Lose Muscle?

Possibly even more rare are the situations where someone wants to lose muscle.  Frequently these are ex-athletes who have no desire to maintain their muscle mass once their competitive days are over.

More commonly are athletes for whom losing muscle mass may actually improve performance.  Generally these tend to be endurance athletes who, for some reason, gained excessive amounts of muscle mass (either deliberately or through involvement in another sport) often in non-functional muscles.

A big upper body is typically a hindrance for an athlete such as a road cyclist since it’s just dead weight to be hauled around the course.  Losing it may improve performance.

In this vein, there is a story that is often told about Lance Armstrong who, after losing a large amount of weight (including some upper body muscle mass) due to his bout with cancer, was a much better cyclist because of it.  In this case, losing non-functional muscle could only improve his power to weight ratio.

Finally, extremely obese individuals often gain some lean body mass (some of which is muscle) in the process of becoming obese.  Most obesity experts expect, and don’t necessarily mind, that that ‘extra’ lean body mass is lost when weight is lost.  In fact, up to 25% of the total weight lost may come from lean body mass without anybody getting too concerned in that situation.

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