Fat loss in athletes: the best strength training protocol

Body composition is critically important in determining athletic performance. All other things being equal, an athlete carrying less superfluous weight (ie body fat) will always outperform a heavier and ‘fatter’ athlete simply because there’s less weight to move around, resulting in an improved power-to-weight ratio. This in turns means that an athlete who sheds some excess body fat will improve their power-to-weight ratio - without needing to increase aerobic power, with all the extra training demands that would entail.

Conventional thinking

The conventional thinking about fat loss and training is that steady-state moderate-intensity aerobic exercise is the best route to reducing body fat. There are two reasons for this; firstly, the amount of energy (calories) expended per hour during aerobic type activity such as running, swimming, cycling, rowing etc is relatively high – typically ranging from 600-1,000kcals per hour depending on athlete fitness and level of exertion⁽¹⁾. And since moderate aerobic activity can be continued for a significant period of time (up to two hours or more), the total calorie burn can be very significant. A second reason is that as long as there’s ample oxygen available to working muscles - ie the athlete is not working at or near their maximum oxygen uptake limit (VO2max) - fat oxidation can contribute a major proportion of this energy demand⁽²⁾.

Adding resistance to aerobic exercise

While the importance of aerobic training for maintaining or reducing levels of body fat has been confirmed in numerous peer-reviewed studies (have you ever seen a fat ultra-marathon runner?), athletes frequently but anecdotally report that when resistance training is added to an existing aerobic program, further and significant fat losses are observed, which are greater than those occurring simply by adding in extra aerobic training. In other words, resistance training itself seems to provide an additional mechanism for fat loss. It turns out that these anecdotal observations are indeed well founded and supported by good evidence.

Firstly, we now know beyond doubt that resistance training alone can improve body composition by increasing lean muscle mass and reducing body fat. For example, a large systematic review study published in 2021 reviewed a large number of previous studies and concluded that all forms of resistance training, but particularly forms where resistance exercise were completed in rapid succession (eg circuit type training) significantly reduced fat mass⁽³⁾.

However, this still doesn’t answer the question of whether adding in resistance training to an existing aerobic training program can play an additional fat-burning role compared to aerobic training alone. A 2018 review study looked at data from 12 trials involving 555 younger subjects who undertook either concurrent aerobic plus added resistance exercise, or aerobic exercise alone in order to lose body fat and improve key measures of health⁽⁴⁾. Importantly, the exercise volumes were matched. It found the following:

·        Compared with aerobic exercise alone, aerobic + resistance exercise resulted in greater reductions in fat mass.

·        Aerobic + resistance exercise resulted in greater increases in lean body mass (muscle) compared to aerobic only.

In addition, we now have a mechanistic explanation that can explain how this effect occurs. A 2021 study carried out by researchers from the Kentucky College of Medicine and College of Health Sciences studied the phenomenon whereby muscle cells undergoing mechanical loading (ie strenuous resistance exercise) release small particles called extracellular vesicles from the muscle cells⁽⁵⁾. Without delving too much into the technicalities, the researchers discovered that not only were these vesicles released following resistance training, but also that they contained a signalling molecule called ‘muscle-specific miR-1’.

Once circulating in the bloodstream, these vesicles and their cargo of miR-1 were preferentially taken up by fat cells, and once inside the fat cells, the miR-1 stimulated the fat cells to released stored fat and then upregulate fat burning. In short, these vesicles acted like biological messengers to help switch on fat burning in fat cells - regardless of any other type(s) of exercise that take place.

Best strength for weight management

The accumulated evidence that adding in some strength training to an aerobic training program provides an additional and significant fat burning effect is strong, But what type of strength training is likely to produce the best results for athletes seeking to shed a few pounds? To date, the research on this topic has been quite limited, but a new study by a team of Canadian scientists has provided some valuable clues⁽⁶⁾.

Published in the Journal of Strength and Conditioning Research, this study looked at the effects of both low-load and high-load resistance training on post-exercise exercise metabolism over the next few hours – specifically the extra oxygen consumed during the recovery period (due to the temporary increase in metabolic rate that is induced by vigorous exercise) and also the rate of fat oxidation following resistance exercise. In this study, the researchers compared the effects of a low-load, high volume resistance session to a high-load, low volume session, both of which performed to volitional fatigue.