James Krieger on the Issues of Tracking Body Fat Percentage

On this episode of the Rippedbody Podcast, I interview James Krieger. James is a published scientist, author, speaker, fitness competitor, statistical wizard and the mind behind the immensely popular blog and membership site, Weightology.net.

We discuss the different methods available for tracking body fat percentage [06:15], the two-component model used by BIA machines [14:00], my secret method to cheating on a B.I.A. scan [22:10], carb loading [29:30], and how to successfully assess your progress [44:00].

James is a wealth of knowledge and we cover a really broad and interesting range of topics in this great chat.

Selected links

Show notes

  • James is a statistics wiz. He runs a website called “weightology.net”. Andy feels like these are some of the best articles on the internet and you don’t need to be a professional to understand them. James Krieger is also a great debater. [00:20]
  • On Weightology.net, the post that gets the most hits is the insulin hypothesis of obesity. Today, Andy wants to dig into body fat measurement. But, in order to measure your body fat percentage, you need to be dead. [3:00]
  • The only way to measure your body fat percentage accurately is through dissection. The analogy to a weatherman predicting with a margin of error. Body fat is really just a prediction of what we think your body fat percentage is. [4:30]
  • Methods for measuring body fat percentage. First is hydrostatic or underwater weighing. DEXA is another method, a type of x-ray beam which measures lean vs. fat mass. Biometric / Bioelectric impedance puts a small electrical current through your body. Bodpod, similar to underwater weighing, uses air displacement. There is a new one, the use of ultrasound (not many studies). Skinfolds, plug the numbers into an equation. Body Mass Index can be an estimate of your bodyfat percentage, but it is very crude. [6:15]
  • James is not a fan of most measurements. Not against taking the measurements, but understand the limitations of the numbers you are getting. Hydrostatic weighing or DEXA are the best options available to an individual. He suggests to really take a long time between measurements. The error rates are actually bigger than the difference you will see in a few weeks. Look at a time scale of three months to six months. The next best option would be skinfold measurements. The worst is BIA. As for the Bod Pod, it does as well as hydrostatic weighing. [9:10]
  • Why the Bod Pod isn’t as good. – Issues include body hair will impact measurements and the type of suit you wear. Additional factors really impact the accuracy. [12:50]
  • The Two-compartment model and BIA Machines. For the most part, stay away from BIA machines. When you test people on a BIA device, you could visibly see people have lost body fat percentage yet the BIA device would say they gained body fat. Body Mass Index and BIA are fairly comparable in accuracy. [14:00]
  • The electrical current will take the path of least resistance. It can very easily miss areas. There are different equations for different groups of people. However, only when looking at larger groups, the errors can almost cancel each other out. [17:30]
  • BIA machines can ding people’s motivation or create false motivation. A mental rollercoaster. Most people don’t realize the margin for error. [19:00]
  • If you want to see a fat-free mass increase in DEXA, carb load before your scan. If you weigh yourself daily, you’ll see your numbers fluctuate with water. [19:55]
  • Taking weight first thing in the morning and average it over seven days. [20:45]
  • How to cheat a scan. – Have a really fatty large meal and dehydrate. Carb load and hydrate which increases fat-free mass. [22:10]
  • How much could you swing a BIA? 5-10 lbs of swing in weight could translate into a 10 point swing. With error, 5-6% in a matter of days, using a bunch of tricks. Realistically, it would take a 2-3 month period to see this change. [24:10]
  • James first men’s physique show. James was in a calorie surplus at his first weigh-in. He didn’t account for losing fat-free mass due to the loss in body water. He overestimated his target weight. There is a loss of body water when people begin to diet. [26:40]
  • Carb-loads and cheating. – Carb deplete first, go on a low carb diet, go on a high rep metabolic training plan to deplete glycogen. Glycogen = carbs in your muscle tissue. How much water is in your muscles affects how ‘full’ you look. Then, carb-load, very high carbs, and very low fat. Adding extra salt or high sodium foods (processed foods), causes you to hold a bunch of water. Restaurant meals are very high in salt. [29:30]
  • Andy’s secret recipe to cheat on a BIA measurement. [32:10]
  • “CheatYourBodyFatTest.com” Let’s get this setup. [33:00]
  • Back to two-compartment model – separate into fat mass and fat-free mass. DEXA is a three compartment model, adds bone mineral. Four compartment (gold standard) is bone mineral, body protein (i.e muscle mass), body water, body fat. DEXA can’t determine the difference between water and body protein. A four-compartment model can only be done in a research lab, and even at that, it is expensive. Not many studies use the four-compartment model. [34:40]
  • BIA in research is still useful in group studies. Not all BIA machines are made equal. [38:30]
  • Inbody: Any BIA machine will have an error. [41:00]
  • You don’t have any control of the hydration of fat-free mass. There is an assumption that the fat-free mass has a certain hydration. However, research does that hydration changes with fat gain and loss. [42:20]
  • Assessing progress and finding the best methods. Are you maintaining performance? However, things like leverage come into play. Certainly better than body fat on a week to week. Waist, hip, and general circumference is a good metric. However, circumference on a week-to-week might not be helpful, but monthly. Pictures as a visual representation of yourself are a good indicator. Skinfold can be helpful (not every week) if you get the same person taking the measurements. While body weight doesn’t tell you everything, it is useful (consider experience, ability to keep strength while losing weight), weekly averages. [44:00]
  • Andy’s Free Diet Guide.  [48:00]
  • The future of James Krieger. Website revamp with modern standards. Restarted his research review. May start some online coaching. More research studies, running stats, more publications. Talks in Washington, Norway. [49:50]
  • Membership section with research and question section on Weightology.net. Video seminars and lectures. Feature article content. $11.99 USD / month. [53:00]
  • Reading opinions versus reading the information directly from the researchers. This is an incredible value James provides to people interested in health and fitness. [56:00]
  • One wish for the fitness industry and human nature. As an evidence-based person, the general human tendency to want quick fixes, falling victim to bullshit. James wishes human nature would change. He hopes more people appreciate the evidence-based approach. It takes a lot of education and continual learning. He thinks we should always hunger for more knowledge and acknowledge the limits of our knowledge. [57:30|
  • If something looks too good to be true, it probably is. [1:01:00]

Thank you for listening! – Andy and James


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About the Author

Andy Morgan

Hi, I'm Andy, co-author of 'The Muscle and Strength Pyramid' textbooks and founder of RippedBody.com. This site is my sincere effort to build the best nutrition and training guides on the internet. Some readers hire me to coach them, which I've been doing full-time, online, for the last seven years. If you're interested in individualized, one-on-one coaching to help you crush your physique goals, let's start the conversation. (You can read more detailed bio here.)