Not all weight loss should be considered successful. A
successful weight loss should be judged taking into account several factors
such has the ratio of fat to lean mass lost - in other words, in a successful diet lean mass losses should be kept to a
minimum. Exercise, especially weight training, can and should be used to offset
lean mass losses during a diet, and in some cases make you lose fat and gain
muscle at the same time.
One study assessed the individual and combined effects
of weight loss and weight training
on body weight and body composition for 8
weeks (1). Forty obese women
were randomly assigned to 4 groups, a control (C); diet without exercise (DO);
diet plus weight training (DPE); and weight training without diet (EO). Baseline caloric requirements were estimated and then
reduced by 1000 kcal/d. The
nutritionally balanced diet consisted of 50% carbohydrate, 27% protein, and 23% fat and included a
daily protein supplement. C and EO
subjects were instructed to maintain their normal
caloric intake. Protein supplements were given to the two
diet groups to ensure protein intake ≥ 1.0 g/kg body weight.
The weight training routine included the following
exercises: bench press, inverse leg press, lateral pull down, biceps curl, triceps
extension, calf raise, leg extension, and hamstring curl. Subjects went
to failure on the third set: the
exercise supervisor and the subject’s partner provided strong verbal encouragement during the final phase of the third set,
and the subject’s partner helped
lift the weight past any momentary weak points in the final set until the subject was unable to voluntarily complete another repetition.
Body weight
decreased for all dieting groups, except for the exercise only group. Body weight
decreased more for the diet only group (-4.47 kg) followed
by diet plus weight training group (-3.89 kg) and the control group (-0.38 kg).
The exercise only group gained a little weight (0.45 kg).
More importantly, lean body weight (LBW) increased
with exercise only (1.07 kg) and
diet plus weight training (0.43kg),
compared with a decrease for diet only
(-0.91 kg) and control (-0.31 kg). Upper-arm
muscle areas increased for all groups with the greatest increase with diet
plus weight training (11.2 cm2) and exercise only (10.4 cm2) compared with
control (2.7 cm2) and diet only (2.1 cm2). In percentages of total body weight
loss, diet only group lost
about 20% LBM, and diet plus
exercise lost 11% LBM. This study therefore concluded that adding weight training exercise to a
caloric restriction program with 27% protein (≥ 1.0 g/kg) results in maintenance of LBW compared with diet only
(1).
Increases in bench press strength were also
observed with diet plus exercise (+5.31kg), with exercise only (4.77kg) and for
the control (1.13kg), and a slight decreased with diet only (-0.69kg) after 8
weeks.
Other studies
observed the same degree of LBW increases with exercise following an energy
deficit. One study reported LBW increases of 0.5kg (2) and another reported an increase of 1.2 kg (3) over
16 and 17 wk, respectively. In the second study with 22 obese women (3), increased physical activity consisted of jog-walking
2.5 miles and 1 hr of calisthenics/week. Caloric restriction was
self-determined and was generally moderate, accounting for about 60% of the
total mean energy deficit. Importantly, many
of the women had failed at previous attempts to lose weight by dieting alone.
However other
studies reported loss of LBM even with exercise (4,5,6,7). Maintenance or even
gain of LBM can be achieved with caloric restriction with aerobic (2) and
weight training (1,3), although the mechanisms may be quite different. Maintenance of LBM may result from increasing the proportion of calories
expended as fat and reducing the
need to deaminate amino acids to supply carbohydrates or through muscle use (2).
Losses of LBW expressed
as a percent of total weight lost have ranged from as little as 15% for mild caloric
restriction (1,800-kcal) (8) to as high as 30-80% during semistarvation
(600-800kcal) followed by 16 days of total starvation and 7 days back to the
restricted diet (9) and 80% of maintenance calories or 600-1000kcal per day (4).
Diet-induced weight
lost as FFM and fat mass is similar between older obese men (10) and obese women
(11) compared to younger adults (11,12). As noted
above, negative caloric balance induced by exercise or in combination
with caloric restriction appears to minimize losses of LBM (1,2,3). Adding endurance or
resistance exercise training to a diet program helps preserve FFM during weight
loss (13,14,15,16).
A meta-analysis of studies
conducted primarily in young and middle-aged adults also found that exercise reduced the percentage of weight
lost as FFM from 22% in women and 29% in men to 17% for both women and men (17).
Obese older subjects were
subject of 6 months of weekly
behavioral therapy for weight loss in conjunction with exercise training 3
times per week (18). The diet contained approximately 30% of energy as fat, 50%
as carbohydrate, and 20% as protein.
Total calorie intake was adjusted to prevent more than a 1.5% loss of body weight per week, with the goal of 10% weight loss at the completion of the
study. The exercise program focused on improving flexibility, endurance, strength,
and balance. They lost about 8.4% of body weight without a change in fat-free mass. Additionally, compared with the
control group they lost fat (-6.6kg) whereas the control group gain fat (1.7kg)
(18).
Conclusion
The ability to lose fat and gain muscle at the same
time in a caloric deficit is usually seen in the untrained obese, but as we
will see in a future article it can be done for the trained athlete as well.
Other
factors will be discussed in the following articles, such as protein intake in
a caloric deficit and the rate of weight loss. Finally, another feature of a successful
diet comes in a long-term, the dieter should be able to maintain the weight loss
(fat) and avoid fat regain.
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Summary of all articles on
Exercise and nutrition
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