Contrary to what the infomercials suggest, there is no such
thing as spot reduction. Fat is lost throughout the body in a
pattern dependent upon genetics, sex (hormones), and age. Overall
body fat must be reduced to lose fat in any particular area.
Although fat is lost or gained throughout the body, it seems
the first area to get fat, or the last area to become lean, is
the midsection (in men and some women, especially after menopause)
and hips and thighs (in women and few men). Sit-ups,
abduction, etc. will only exercise the muscles under the
Performing lighter weight with more
repetitions (15-20 reps, 20-30 reps, or 20-50 reps) does not
burn more fat or tone (simultaneous decrease of fat and increase
muscle) better than a heavier weight with moderate repetitions
(8-12 reps). Weight training utilizes carbohydrates after the
initial ATP and CP stores have been exhausted after the first
few seconds of intense muscular contraction. Typically, a set's
duration is 20 to 30 seconds. For the average fit person, it
requires 20 to 30 minutes of continuous aerobic activity with
large muscle groups (e.g. Gluteus Maximus and Quadriceps) to
burn even 50% fat; fat requires oxygen to burn. Performing a
few extra repetitions on a weight training exercise is not significant
enough to burn extra fat and may in effect burn less fat. If
intensity is compromised, less fat may be burned when light weight
is used with high repetitions. The burning
sensation associated with high repetition training seems
to be the primary deterrent for achieving higher intensities.
Higher volume weight training (i.e. 3 sets versus 1 set of
each exercise) with short rest periods of approximately 1 minutes
can stimulate a greater acute growth hormone release (Kraemer
1991, 1993; Mulligan 1996). Growth hormone is lipolytic in adults.
It is hypothesized that maximal effort is necessary for optimizing
exercise induced secretion of growth hormone. Growth hormone
release is related to the magnitude of exertion (Pyka 1992) and
is attenuated with greater lactic acidosis (Gordon 1994).
Intense weight training utilizing multiple large muscles with
longer rest between sets may also accentuate body lipid deficit
by increasing post training epinephrine. Intramuscular triacylgycerol
is thought to be an important energy substrate following repeated
30 second maximal exercise with 4 minute recovery intervals (McCartney
1996, Tremblay 1994). Rest periods lasting approximately 4 minutes
between maximal exercise of very short duration is required for
almost complete creatine phosphate recovery required for repeated
maximal bouts (McCartney 1986). Insufficient recovery may compromise
the intensity of the exercise and in turn, possibly decrease
intramuscular triacylgycerol utilization following anaerobic
exercise with significantly shorter rest periods.
For individuals attempting to achieve fat loss for aesthetics,
the intensity of weight training can be a double edge sword.
When beginning an exercise program, muscle mass increases may
out pace fat losses, resulting in a small initial weight gain.
Significant fat loss requires a certain intensity, duration,
and frequency that novice exercisers may not be able to achieve
until they develop greater tolerance to exercise. If an exercise
and nutrition program is not adequate for significant fat loss,
a lighter weight with higher repetitions may be recommended to
minimize any bulking effects, although less fat may be utilized
hours later. If an aerobic exercise and nutrition program is
sufficient enough to lose fat, a moderate
repetition range with a progressively heavier weight will
accelerate fat loss with a toning effect. If a muscle group ever
outpaces fat loss, the slight bulking effect is only temporary.
For a toning effect, fat can be lost later when aerobic exercise
can be significantly increased or the weight training exercise(s)
for that particular muscle can be ceased altogether. The muscle
will atrophy to a pre-exercise girth within months. Higher repetitions
training may be later implemented and assessed.
It still may be recommended to perform high repetitions (e.g.
20-30) for abdominal
training. It has been theorized muscular endurance may be more
beneficial for lower back health than for muscular strength.
Furthermore, moderate repetitions with greater resistance can
increase muscular girth under the subcutaneous fat, particularly
in men, who have greater potential for muscular hypertrophy.
Increasing the thickness around the waist with existing abdominal
fat may further increase bulk, particularly in men who typically
have greater intra-abdominal and subcutaneous fat in this area.
The abdominal musculature is composed of relatively small muscle
mass as compared to the glutes, quadriceps, hamstrings, chest,
and upper back. Performing high reps with a lighter resistance
should not compromise metabolism or muscle increases, as would
performing high reps with light resistance on other, larger muscle
groups. See Spot Reduction Myth
It is plausible that the high repetition myth was originated
and later propagated by bodybuilders
that used calorie restrictive diets to shed fat before a
contest. Because of their weakened state from dieting, they were
unable to use their usual heavier weights. When asked about their
use of lighter weights, they explained they were "cutting
up" for a contest. This is merely a theory, but it is easy
to see how it may have been misunderstood that the lighter weight
was used to reduce fat, instead of actually being a result of
their dietary regimen.
Typically, with weight training alone, the fat loss is equal
to the muscle gain, give or take a few pounds. Certain dietary
modification can have much greater impact on fat loss than with
weight training alone. The ideal program for fat loss would include
the combination of proper diet, weight training, and cardio exercise.
Also see study summaries: Weight
Training and Diet and Endurance
and Weight Training.