August 2024

Calories In is a really interesting problem, you would think it just comes down to measuring how much food is taken in but when you calculate fiber, mis-measurement, and or use a misleading app, trying to calculate that 500 calorie per day deficit for that 1 pound per week weight loss becomes very hard, or even impossible.

Actual Burned Calories

The amount of food you eat that gets converted to useful energy, and is apart of the metabolic process of converting glucose to CO2, Water and ATP (Energy) or converting fatty acids to CO2, Water and ATP. You can see the chemical equation for glucose below:

Glucose Formula C₆ H₁₂ O₆ + 6O₂ →6CO₂ +6H₂O+ATP (energy)

The interesting part is the human body is only about 25-30% efficient in doing this conversion, the rest is lost to heat or other metabolic processes. Additionally based on what you eat, when you eat, wether you are dehydrated or well hydrated this number can fluctuate. This is really important as sometimes the less you eat, the more efficient you get at converting this energy and the less heat you produce. Think about it, if our ancestors were not able to get more efficient, humans wouldn’t have survived when there were food shortages or the hunts didn’t go as expected.

Accuracy of food measurements

How many of you use a scale to measure the amount of food you are consuming? How many of you just use the serving size count on the box? While the serving size is fairly accurate, unless you’re measuring this to the gram it’s very hard to measure. Additionally if you use a recipe combining all the ingredients the amount of oil, and understanding the exact portions makes it very difficult. Bottom line it’s easy to go 10% over here 10% over there, before you know it that 500 calorie deficit is actually just 100 or even over your daily caloric maintenance goal.

The App Illusion

While Apps do provide accurate measures in some cases, some entries are crowd sourced. Take for example type “chicken breast” into your favorite calorie app or book. In a very popular app I received 10+ results. Was this fried, raw, baked, measured by “medium or half of a breast” or ounces or grams? Was it natural or full of saline? The measurements of raw skinless boneless chicken breast by the USDA per 100g is: Protein 23g, Fat 1g, Carbs, 0g, Total calories 107. The measure for cooked chicken breast by the USDA 100g is: 31g of protein, 3.5g of fat, 0g of carbs for 165 calories total. This is a difference of 54%. If you’re trying to count calories and measure the wrong thing there’s a high chance of error, also, who eats 100g of chicken breast in the US?

In conclusion there’s a lot that go wrong even with technology and dedication.

Taking a short break from technology and building things to talk about fitness and weight loss. I’ll present a 3 part series of posts to talk about what I’ve learned over the past few years.

RMR Oxygen and CO2

There’s been a lot of books I’ve read over the years about losing weight and getting fitter. Low Carbs. No Meat. 10,000 Steps. Count Calories. But it wasn’t until I went to have my Resting Metabolic Rate (RMR) measured that I truly woke up to the real science of metabolism and weight loss.

A metabolic cart does something real simple, it measures Oxygen (O₂) In and Carbon Dioxide (CO₂) Out. It does this for about 20 minutes and then it inputs the results into the Weir Equation and calculates your calories per minute. See Below:

Weir Equation is EE (kcal/min) = (3.941 x VO₂) + 1.106 X VCO₂)

To substitute my measured numbers (3.941 x .354L/min + 1.106 x .292 L/min) ~= 1.718 * 1440 = 2474 calories / day

Fascinating. Metabolism is really just about how much O₂ you breathe in and how much CO₂ you breathe out. But while I found this super helpful, what about all the folks that say steps per day or you must do cardio? Well this is a little more complicated but it still all comes back to Oxygen.

METs or Metabolically Equivalent Task

A MET or Metabolically Equivalent Task. This is defined as 3.5 milliliters of oxygen per kg of body weight per minute. Now this will vary per person and some people will burn more oxygen per minute some will burn less based on fitness level. Here are some sample MET values below.

Activity	METs
Walking 3mph, 10 minute mile	3.5
Running 6mph, 10minute mile	9.8
Bicycling 10-12mph	6.8
Swimming freestyle	7.0
Weight Lifting	3.0

So the equation for this is below:

Calories Burned = MET value x body weight in kg x duration in hours

Keeping Math Simple, walking 20min/mile pace yields, 3.5 Mets x 100 kg x 0.333 = 116.55 calories per 2000 steps.
Subtract your RMR from this number, so at rest a 100kg person burned 34.32 calories, for net gain of 82.335 calories per 2000 steps.

So the cardio crowd or the 10,000 steps crowd wasn’t wrong. A 100kg person will burn 82 more calories per 2000 steps walking than sitting on their butt. But if your fitness tracker or your treadmill typically has these numbers in the 150s or 200s per 20min it’s way off.