Form vs. Function: How Much Does Body Composition Matter?


How much does body composition (aka body fat percentage) really matter? That depends on what your goals are. I know, I know…you hear that from me a lot. But it’s true!

On the high end, excess body fat is linked with just about every chronic disease state, from high blood pressure to cancer to diabetes.  And it sure makes exercise and even daily living a whole lot tougher. Can we agree that this is not a good thing?

On the low end, essential fat levels refer to “danger zone” ranges where your health and performance will likely be affected.  Generally accepted essential fat thresholds are around 3-4% for men and 12-13% for women, give or take a point.  Body builders may go there for short periods for competition. Just because it’s possible does not mean it’s good for us; hungry all the time, grumpy, lousy concentration, no interest in sex, chronic fatigue and intolerance to cold are some of the tradeoffs for that extreme muscle definition. And for women the effort it takes to reach very low body fat levels may lead to the female athlete triad , comprised of disordered/restrictive eating, low bone density/ osteoporosis and loss of regular menstrual cycle.

The ACE (American Council on Exercise) provides us with guidelines that are widely accepted and a good place to start:



A few other factors to consider:

  • Women naturally have higher body fat levels than men at any given fitness level.
  • Genetics play a role in where we accumulate body fat and what body fat level we can maintain long-term.
  • Body weight does not necessarily reflect body composition. There are plenty of “skinny fat” people running around out there.

So do we even need a number? Not necessarily. I do body fat assessments with my clients because it gives us another tool to work with, but we don’t use it as the only measure for change.  First of all, short of underwater weighing, most methods (BIA, calipers, even Dexa scans) have a significant range of error. And second there are simple real-world ways to evaluate how you’re doing…like looking in the mirror! Marc Perry at www.builtlean.com has done an excellent job of summarizing body fat levels in this article. He’s paired each level with photos for visual reference.

Don’t neglect performance as a measure. Ultra-low body fat does not always equate to strong and fast. Take a look at some of last year’s Games athletes heading into the water for the start of the tri (photos from www.crossfit.com).  We know they are crazy fit but are they anywhere close to the “shredded” look of body builders in a competition? Heck no!  If an ultra-low body fat would help them win the Games would they do it? Heck yea! I’m sure the majority of them have experimented with body composition to find the optimal level for performance.

pc2     pc3


So whether you go by numbers, appearance or performance, what is right for you? Let’s check in with a few fictional characters at the local Box for some insight. Disclaimer: All are complete fabrications of my imagination vs. actual athletes…although you might relate to one or more of our friends here!

  • Steve Sedentary is brand new to CrossFit, or any exercise in the past decade for that matter, but is excited to get started. He tests out at 30% body fat, which is quite high for a guy. For him reducing his body fat is important for his overall health and will significantly improve his ability to enjoy exercise and daily activities as well as improve his appearance. He does want to improve at CrossFit and build muscle mass but his primary goal is to “lose weight” which equates to losing body fat.  PRIORITY: HIGH FOR FAT LOSS. STEVE NEEDS TO BE AWARE THAT DIET TO DROP FAT MAY NOT OPTIMIZE PERFORMANCE IN THE SHORT-TERM.


  • Rachel Regionals is a hard-training talented CrossFitter whose goal is to make it to Regionals within 2 years. She tests out at 19% body fat. She’s tried in the past to lose more fat but finds that her strength numbers drop and she runs into problems with fatigue especially on Day 3 of her 3 on/1 off training cycle PRIORITY: HIGH FOR MAINTENANCE, LOW FOR FURTHER BODY FAT REDUCTION-FOCUS ON PERFORMANCE FIRST AND MAINTAIN CURRENT BODY FAT LEVEL For Rachel she should continue to focus on performance, working to find the ideal balance between maintaining pure strength to handle heavy Oly and power movements and maximizing power-to-weight ratio for pull-ups, handstand push-ups and running.  Check out this discussion about performance and body composition from Keith Norris down in Austin and this clip of Keith at PaleoFX this year, discussing body composition for female collegiate athletes (hint: U of Texas collegiate sprinters/volleyball players run around 20%).


  • Bill BeachBody’s primary focus is lookin’ HOT with his shirt off. He does not care about his Total or his Fran time. He is all about the six-pack…and to uncover the six-pack he’s got to drop down to a pretty low body fat level, probably in the 7-8% range. PRIORITY:  HIGH FOR FAT LOSS.  MAY BE UNSUSTAINABLE LONG-TERM. USE CAUTION – COULD LEAD TO DISORDERED EATING IF HE BECOMES OBSESSED WITH A PURSUIT OF AN EVER-LOWER NUMBER.  OVERRESTRICTION COULD RESULT IN LOSS OF MUSCLE MASS.


  • Betsy Back-in-the-Game has been CrossFitting for 3 years but life took over for the past 3 months; she didn’t work out much and strayed away from her usual 90% Paleo diet.  She lost muscle mass during her hiatus and her body fat is 23%, up from her usual 20%.  Based on past experience she knows she feels and looks great, performs well and can maintain at the 20% level but she is equally focused on bringing her performance back up to speed because she’s signed up for a team competition in 3 months. PRIORITY: SHE NEEDS TO PRIORITIZE HER GOALS FIRST.  RESTRICTING CALORIES/CARBS TO DROP FAT MAY HINDER TRAINING FOR PERFORMANCE. SHE MIGHT OPT TO FOCUS ON BODY COMP FOR A MONTH THEN SHIFT GEARS AND ADD MORE CALORIES/CARBS FOR THE NEXT 2 MONTHS TO RAMP UP HER TRAINING.


This brings me to why I threw in a picture of Linda Hamilton (as Sarah Connor in her Terminator film role)…SUSTAINABILITY.  By the way, – if you haven’t seen Terminator 2 she was bad-ass! I saw an interview years ago where she talked about the intense training, restrictive diet, etc. that she followed to get the muscle definition (read low body fat) that everyone was raving about. And that it was damn hard and, for her, unsustainable for the long-term.  As CrossFit athletes we are no strangers to hard work and intensity; the pursuit of tough goals is part of our daily lives. But I encourage you to seek some balance. If your only focus is appearance or pursuit of a number on the body fat scale and your overall quality of life or your health is suffering because of it, you might want to reevaluate your priorities. What good are those defined muscles if you don’t have the energy to get to the Box for a WOD?


Bottom line…prioritize your goals, be realistic in your expectations, work hard but consider sustainability, and balance performance and appearance goals.


See you at the Box!  Karen