Metabolic Efficiency

What can Metabolic Efficiency do for you: a Case Study

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I reported a while back on Metabolic Efficiency (ME), how it works and its effect on health and performance. Metabolic Efficiency is the body’s ability to burn more fat instead of carbohydrates for the same intensity. It is trainable with nutrition (75%) and  training (25%). In that earlier post, I had also given an example of two athletes and how different they were and how that would impact their racing nutrition. Today I would like to talk about one athlete that went through a Metabolic Efficiency training and how it impacted her.

First the introduction. We’ll call her Jen.


  • Over 50, Age Grouper, Female
  • Long time casual but committed athlete, triathlon about 10 seasons
  • Not overweight
  • Cholesterol – borderline/ high / creeping up in recent tests

Jen came to me very frustrated. She wondered if her self-directed nutrition “formula” was holding her back from performance improvements (i.e. ability to sustain energy levels during longer trainer runs without GI discomfort, and ultimately, race specific improvement). If she followed the gel package instructions (one gel every 45 minutes), how could there be GI issues?


  • Eat more protein – range depending on daily plan of activity/exercise
  • Eat protein and fats with carbohydrates, which led to a decrease in overall carbohydrates.
  • Match carbohydrate intake during exercise to effort level and amount her body could absorb without distress.


  • Decrease requirement for nutrition during training and racing
  • Improved training performance
  • Improvement in Metabolic Efficiency- pre-intervention, burned 98g /hour carbohydrate for her 70.3 effort, post intervention, 42g/ hour. A huge improvement.
  • Weight loss (7%) and fat loss
  • Lower cholesterol


The first thing we did was a nutritional analysis. Jen had pretty good eating habits. She was at a healthy weight too. She did not eat excessive processed foods,except for the sports nutrition product whether bar or gel here and there. She took in the gels in the amount and frequency recommended on the package. She also was pretty good at eating her fruits and vegetables. But, she loved her pastas and breads, having grown up in an Italian home!

Overall on a typical exercise day lasting 1 hour in the day, she would eat 2200 kcal. I was actually surprised, this was a lot for a small woman like Jen. It turns out that when we tested her on the metabolic cart, her energy expenditure at rest is 1500 kcal. On average for a women her age and height, I had calculated 1200kcal. So a 300 kcal difference is huge. That is why using average especially for athletes,  is not always optimal and that is what most apps use. Jen is definitely one of those lucky lady always full of energy who can eat pretty much anything and won’t gain much weight!

Her macronutrients breakdowns showed up to be 75g fats, 300g carbohydrates and 92g protein. Pretty typical American diet.  She was mostly a sugar burner, and therefore needed more carbohydrates during a race, which could eventually lead to GI distress.

Her Metabolic Efficiency test confirmed that. In  this first graph, we see her cross-over from fat burning to sugar burning is at 1.9W/kg, which for her is 95 Watts and corresponds to her Zone 1 or 2 approximately or fairly easy effort for her. So for her 70.3 effort at about 2.4 W/kg she would burn 98 g/hour of carbohydrate, which is definitely a lot!

Graph 1: Jen metabolic efficiency results pre-intervention. Here it is reported in Watts/kg versus % of Fat (red) versus Carbohydrates (blue) burned.

Also Jen shared with me her blood test results and her total cholesterol was at at 230 while her LDL (bad cholesterol) was at 130 and HDL (good cholesterol) was at 76. Her total cholesterol was a little high as well as her LDL by current standard, the ratio of total to HDL was still pretty good.

We worked on Jen’s nutrition with the goal of improving her Metabolic Efficiency.  How? We tried to pair her carbohydrate intake with protein and fats. At the same time, we reduced the amount of carbohydrates a little bit and increased her protein and good fat intake. It took a couple of months of tweaking to finally nail things down. This is what she reported six months later:

“Today I ran 1:40, 11 + miles. At 7 am I ate one toast w butter, 1 hard boiled egg and about 4 spoons of plain fage yogurt with a tsp of honey. A little milk in about 4 oz of reg coffee. I drank about 20 – 24 oz of water during the run and ate only one (not a package) clif block (30 calories at 1:18 mark. I didn’t really need it but it was there so I ate one). I was totally fine energywise. Really good news after I struggled last year by eating too many carbs at once from those gels and not feeling well. Whoopee.”

In the process she lost a eight pounds, which on her petite physique was huge. Her % body fat remained healthy. She also had a reduction in her total cholesterol (215), her LDL cholesterol (109) and her good HDL cholesterol raised a little bit to 81. Her doctor was happy and stopped badgering her about taking statins.  

Now, how was her Metabolic Efficiency test? Again we tested her on the bike using a similar protocol.

Graph​ ​2:​ ​Jen​ ​metabolic​ ​efficiency​ ​results​ ​post-intervention.​ ​Here​ ​it​ ​is​ ​reported​ ​in​ ​Watts/kg​ ​versus​ ​% of​ ​Fat​ ​(red)​ ​versus​ ​Carbohydrates​ ​(blue)​ ​burned.

Her crossover was now at 2.4W/kg (approximately 140W). She improved by 45 W! Now if we look at the amount of carbohydrate she burns at 2.4 W/kg (her 70.3 pace) remember that she used to burn 97g/hour and now gets by with 42g/hour of carbohydrate. If you take into account that a women like Jen might have at the most 300g of carbohydrate stored in her legs, she would last no more than 3 hours without feeling the need to significantly slow down, now she lasts much longer and could potentially go faster. And she did. She PRd at her next 70.3.

And all this just by making some modifications to her diet that would allow her body to learn to burn more fat. It is not even low carb by any means since Jen was still eating about 100-150g of carbohydrates per day and even more on days where she exercised a lot.

Good job Jen!

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