There are many different paradigms for exercise, including resistance training, depending on the end goals.
It has been supposed, that the most effective type of resistance training for fat loss would be that requiring aerobic energy use, e.g. Circuit training. Circuit training is the combination of a range of exercises carried out with light weights but with many repetitions to increase aerobic benefit. There seems to be little argument that this form of exercise would have fat burning benefits. Because it also involves muscular resistance, it could additionally provide metabolic benefits if in no other way than in reducing the loss of muscle mass that may occur through diets alone.
The main questions that remain about circuit training are the appropriate duration, intensity and frequency for optimal fat loss. Based on substrate utilisation, it would appear that the intensity should be moderate (i.e. around 40-60 per cent V02 max), and the duration as long as possible. Because many muscle groups are thought to require at least 48 hours to recover from the micro-cellular damage that results from resistance exercises, it would be inadvisable to carry out circuits, at least with high resistance, on a daily basis. Yet significant fat loss requires regular physical activity over long durations, so circuit training should be combined with other aerobic activities, such as walking, at least on every other day, but possibly also on circuit training days.
Metabolic changes due to muscle gain or maintenance might be expected to take two forms. In the first place, if there is a gain in muscle size in resistance-trained obese people, there is likely to be a gain in energy use due to this increase. Several studies have shown an increase in muscle size, or at least a maintenance of muscle mass due to resistance training in obese people, with or without energy restriction. The increased effect on energy use, however, should not be expected to be great.
The second form may be more important, i.e. the reduction in decline of metabolism that would be expected to occur with loss of total body mass due to food restriction. This can amount to between 5-25 per cent within three weeks on a program using diet alone. If this decline is arrested by resistance training, as it has been shown to do with aerobic exercise, it could have a significant impact on total fat loss. However, to date the appropriate research has not been done in this area.
It is important to point out here that because we are talking about increasing, or at least maintaining muscle mass, this is likely to be reflected in weight gain, even though there may be some fat loss. Hence, use of the scales in this instance is definitely contra-indicated. For most obese people an increase in muscle density and weight, irrespective of fat loss, indicates an increase in body size, which is not generally desired by those looking for a decrease in overall body mass. The main question becomes whether it is more time efficient to carry out long, less vigorous, continuous aerobic exercise in the time that might otherwise be used for resistance training.
In the first place, many obese or overfat people by definition have, or are likely to have, reduced muscular efficiency. They are also likely to have decreased cardiovascular function. Hence, sudden intense activity such as resistance training may be both difficult and dangerous. It would not seem prudent, therefore, to put someone on a resistance training program at the outset of any fat loss regime.
Secondly, there is the issue of motivation. Many people have become fat because of their dislike of the traditional forms of exercise which underly weight training. While they may see themselves walking for fat loss, weight training may not be seen as a preferred option. Third, as mentioned above, there is the question of body perception. Finally, frequency of exercise is important. Because resistance training should not be carried out every day (unless a routine is ‘split1 i.e. Upper body one day and lower body the next), it would be difficult to get the amount of exercise required (without becoming bored) if resistance training only was used for fat loss.
Having said this, it should be recognised that there may be some individuals, men in particular, who would prefer this type of activity instead of, or in addition to, aerobic activity. If so, they should be encouraged to combine both. Fitness centres can no longer expect to maintain their overfat clientele by programming a limited amount of exercise in the gym on alternate days. Consideration has to be given to the individual carrying out their own routines at times outside the gym setting and this should be supported and monitored by fitness centre personnel.
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