DEXA scan showing I gain more muscle when restricting calories. Why?

Question

It's common parlance in the bodybuilding and muscle building world to assume that you need a surplus or diet above TDEE over constant periods called "bulking" in order to build muscle. I refused to do this when I had my first major dietary and exercise changes about 8 months ago. I decided to do a DEXA scan once a month and see what would happen to my body makeup without bulking or cutting, and just eating a calorie range that I feel is right for me to build muscle and lose weight.

The interesting part is simple. Since I wanted to also quickly test the "bulking" and "cutting" theories, I threw in a few days here and there where I would cut and bulk just one or two days per week. Overall, I didn't really "bulk" or "cut" in the traditional sense, but two days before the DEXA scan I would eat high-calorie diets after a brutal, total body workout to see if it made any difference in muscle the prior month. Overall, here's the breakdown:

First month DEXA:

LBM: 133.9 lbs.

BF%: 18.6%

BW: 171 lbs.

Skeletal muscle: ~74 lbs.

Second month DEXA:

LBM: 134.5 lbs.

BF%: 16%

BW: ~164 lbs.

Third month DEXA:

LBM: 135.3 lbs.

BF%: 14.9%

BW: ~157 lbs.

Fourth month DEXA:

LBM: 135.7 lbs.

BF%: 13.3%

BW: ~153 lbs.

Fifth month DEXA:

LBM: 134.2 lbs (lost muscle)

BF% 12.6%

BW: ~149 lbs.

Sixth month DEXA:

LBM: 134.9 lbs.

BF% 13.6%

BW: ~154 lbs.

Seventh month DEXA (big surprise here!):

LBM: 138.6 lbs.

BF% 14.4%

BW: ~160 lbs.

Eighth month DEXA:

LBM: 140.9 lbs.

BF% 14.7%

BW: ~163 lbs.

Skeletal muscle: ~81 lbs.

Basically, I would eat more and LOST muscle at the end of that month -- on another month I ate less and happened to have gained a pinch of bodyfat, but also gained a massive amount of muscle! It would be in the contrary as a 2-day after workout surplus resulted in MUSCLE LOSS and my bodyfat did not increase overall despite this -- and on the gain month, I had a 3-4 day deficit before the scan, which showed more fat but more muscle as well. Overall, cutting/bulking doesn't work for me efficiently since I can gain more muscle in a fast than I had managed in a surplus, all dietary perfections followed with macros and nutrients otherwise, every single day of the challenge.

Answer 1

There's a lot more to the human metabolism and cellular workshop than bodybuilding.com threads are going to get into. Here are some factors you may want to consider.

You didn't discuss your program/training. Some programs are much more mass-building than others. Also, if this was your first exposure to strength training then you are dealing with the "noob gains" category. An untrained athlete could basically throw a telephone book around in a room while fasting and would probably put on some muscle. The things you can do in the first 6-12 months are a lot different than 6-12 years in when you're knocking on your genetic potential.

This line of yours caught my eye:

a brutal, total body workout

There's nothing wrong with total body training, I'm in fact a big advocate of things like Strong Lifts 5x5 and Starting Strength. But the "brutality" in them isn't really about any single day, rather it's the progressive overloading week after week.

Additionally, your metabolism changes as you add increased muscle mass, knocking on nearly 10%. Inversely, the lower your body fat goes the more readily your body will store fat (via increased insulin response).

You, me, and everyone else on the planet shares nearly identical DNA. Our bodies respond pretty much the same way in aggregate, which is why certain fundamentals of fitness and nutrition really are universal. Unless you have a metabolic disease or endocrine issue, there's nothing special or unique about your physiology.

You can't add muscle tissue indefinitely, the rate of your strength and muscle mass gains will drop rapidly, and your body wants to store fat when you get lower. There's no way around this. Rather than try to solve any particular quirk with yourself which is really just an artifact of your first year of lifting (I'm assuming), I'd stick with solid programs and proper nutrition advice.

Answer 2

Replication of pre-test conditions is vital. A DEXA scan interprets water as an organ (or lean mass)

Variables Altering Results

• Hydration Level (or dehydration)
• Glycogen Levels (carb loading vs fasting)
• Time of Day
• Recent Workouts (intensity, timing etc.)
• Recent Activity (simply walking around the room resulted in a 7% change)
• Patient Positioning (baseline vs re-testing)

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DEXA Scan Results
Before vs After drinking a gallon of water:

                    Before Water        After Water      Difference

Total Mass (lbs)    179.6               186.0             6.4
Body Fat (%)        14.6%                13.6%           -1.0%
Fat Tissue (lbs)    26.2                 25.2            -1.0
Lean Tissue (lbs)   145.5               152.9             7.4
Bone Density (lbs)  7.9                   7.9             0.0

Body Fat measurements only changed 1% (seemly a small difference). It’s not.

It also adds 7.4 lbs of "lean tissue" to the results.

The Major Problem

Let’s say after altering your diet / muscle training regimen a repeat scan and finds you’ve gained 15 lbs of "lean tissue".

• Did you gain 15 lbs of muscle?
  
• Or did you gain only 5 lbs and come in with 10 lbs of retained water?

A DEXA scan literally can't tell the difference.

Without the understanding that DEXA has this "water = muscle" limitation - you can easily end up drawing incorrect conclusions about your fitness and diet regimen.

Reproducibility

To obtain accurate results it's vital to control as many variables as possible during the baseline and all subsequent scans. An easy set of conditions to replicate is having all scans done first thing in the morning without eating or drinking anything.

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Source: http://courses.washington.edu/bonephys/opBMDp.html