Exchanging Fat for Muscle

Resistance exercise obviously has more to offer than just size and strength increase. The National Federation of Professional Trainers in cooperation with the Fitness Clinic, a subsidiary research facility conducted a (2) year, limited independent research study. The study involved 40 subjects between the ages of 18 and 35. Among these subjects were resistance and aerobic athletes, general fitness enthusiasts, and overweight housewives and businessmen.

Each subject participated for a period of 30 days. The subjects were randomly placed into two groups. Group #1 performed aerobic activity exclusively, every other day for 30 minutes, at a target heart rate of 70% of maximum. Group #2 performed resistance exercise exclusively, every other day, also for about 30 minutes at 70% average intensity, using a pulling, a pushing, and a leg pressing movement. The sets were of 20-25 reps to unassisted positive failure, performed in a circuit routine. This (3 station) circuit routine was completed 3 times per session.

Both groups were placed on a total caloric intake based on their individual resting metabolic rates (RMR). Each participant’s diet consisted of the same percentages of proteins, carbohydrates, and fats.

Through body composition testing, it was determined at the end of this 30 day period individuals on the exclusive resistance exercise program lost up to 4.5 times as much fat as individuals on the exclusive aerobic exercise program. In addition, some of the individuals on the resistance exercise routine also experienced an increase in total lean weight. In fact, one individual gained 15 lbs of lean weight in this period. This occurred even while on the above restricted caloric intake.

In any case, the average computer sorted results upon completion of the 30 day monitored period, based on body composition testing, are provided here.

Aerobic Group #1:

  1. total weight change…
           6.43 lb. loss
  2. lean weight change…
           2.94 lb. loss
  3. fat weight change…
           3.49 lb. loss

Resistance group #2:

  1. total weight change…
           1.23 lb. loss
  2. lean weight change…
           10.72 lb. gain
  3. fat weight change…
           11.95 lb. Loss

NOTE – It is important to point out that those in group #1 not having prior involvement in aerobic activity experienced faster results than those who had. Likewise, those in group #2 with more conditioned muscle experienced a more conservative and gradual conversion rate.

In laymen’s terms, when the muscle tissues’ energy stores have depleted, the replacement of these stores becomes a priority to the body. During recovery, while on a regular and frequent high complex carbohydrate diet, extra muscular fat must be released and used by the muscle tissue for the necessary ATP production required to fill muscle energy stores back up using the ingested, Insulin-carried complex carbohydrates. The key to resistance exercise and this "fat conversion" is to perform high rep sets at low intensity, over longer periods, with greater frequency. Use basic compound movements because they involve more muscle tissue. This will maximize the depletion of energy, forcing a greater recovery fat release.

The fact also remains, there is a degree of cardiorespiratory enhancement experienced when performing this activity with shortened recovery periods between sets, and by gradually adding to the training volume (adding more circuits,) incorporating this "resistance" activity into your total fat loss program, will prevent significant lean muscle tissue loss.

As a reminder, it is always best to approach your fat loss program with the intention of maintaining or even increasing your lean muscle weight.


These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or [email protected] with questions or for more information.