This blog will be good for anyone who trains or trains people, in weight training.
Despite popular opinion, weight training in itself is no good for fat loss.
There I said it. Allow me to explain. If you aren’t sure about the ‘technical’ terms, which I have kept to a minimum, then check the ‘key points’ which summarise in simple terms.
When I came across studies showing that weight training, in isolation, had no effect on fat loss in the obese individuals being studied, I was a little shocked. I started researching further. And after quite a lot of research I came to the conclusion that in isolation weight training is not effective for fat loss.
Here’s why, in a very brief run down.
Weight training is generally a higher intensity exercise. The muscles are put under strain. I’m going to generalise and discuss the main three muscle fibre types used during exercise. During low intensity exercise type I muscle fibres are utilised. These use fat as their primary energy source and are highly fatigue resistant. This is the type of muscle fibre responsible for doing fast walking or steady state cardio. But this fat comes from the intramuscular fat stores – and not from adipose tissue, which is what we know as ‘fat’.
Increase the intensity and type IIa muscle fibres are called in to help. These ‘burn’ a mixture of fat and glycogen (carbohydrate stores) from the intramuscular stores as fuel. They are less fatigue resistant, and probably are called into play in lighter weight sessions.
Increase the intensity still further and type IIx muscle fibres engage to help the others. These burn glycogen as their primary source of energy and fatigue quickly. These are the muscle fibres recruited during the heavier and more intense weight sessions.
It is to be noted that even at the most intense training the type I muscle fibres are still engaged to an extent. However, the key point is that (and especially when lifting heavy weights), very little of the energy is coming from fat sources, and the actual exercise activity is of (proportionately) a very short duration.
Weight training is carried out in short and sharp sets. These are often taken to failure, or near failure, as the type IIx muscle fibres fatigue quickly. There are longer gaps between sets. The energy utilised is coming from intramuscular fat and glycogen stores – and not our adipose tissue – the visceral and subcutaneous stores we know generally as ‘fat’.
During exercise glucose is released by the liver to start replenishing the muscle glycogen stores and free fatty acids, as normal, are still entering and leaving the adipose tissue. There is very little uptake in the muscles however as the body is in ‘using’ mode rather than ‘storing’ mode, and with weight training very little intramuscular fat is used. Any free fatty acids floating around that aren’t used become re-absorbed by the adipose tissue once more.
KEY POINTS: Weight training is not an effective user of fat as an energy source. The actual exercise duration is too short, and the energy source is mainly carbohydrate rather than fat. And the energy source is provided by the energy in the muscles and not the adipose tissue.
Weight training does however increase EPOC – excess post-exercise oxygen consumption, also known as the ‘after burn’. This is the fabled metabolic increase following high intensity exercise. If you are doing the most intense form of high intensity interval training you may, at the very highest levels, burn around 150kcals additional that day due to the after burn. Most weight trainers would burn substantially less. Though, there is also the issue of where that energy comes from – it is unlikely to be our adipose tissue as we will see.
This is further compounded by metabolic down-regulation. Our body is always looking to maintain homeostasis – balance, between variable operating tolerances. Regularly boost the metabolism with exercise and it will down regulate the metabolism at other times. The energy balance equation works. If you go into calorie deficit, the body will just burn fewer calories. The body is always looking to hold a long term ‘set point’ – yet that is another matter entirely!
Any potential energy deficit created by training, or indeed by bigger muscles, is offset by metabolic down regulation created by physiological and psychological processes to maintain homeostasis. This is the energy balance equation being applied properly. It doesn’t just work one way.
KEY POINTS: Any increases in metabolic rate by the exercise, or increased muscle size, are offset by the down regulation of the metabolism at other times. Balance is maintained within variable tolerances.
The hormone insulin is released following exercise. This is an anabolic hormone and helps the restoring of energy in the muscles for use, regulating the blood sugar, and assisting in the right amino acids (proteins) going to the right places to repair damaged tissue. Insulin helps with recovery. This is why, for sports performance (it doesn’t matter it appears for hypertrophy!) there is a window of 45-90mins where the body optimally absorbs nutrients for use. This is where the supplement market make a killing selling their shakes and potions. Remember that any excess energy, not required to replenish the muscle stores, will be stored elsewhere as adipose tissue.
The problem is that when insulin is present the free fatty acids are blocked from being released from the adipose tissue. Insulin is a storing hormone and not a releasing hormone. So with the fat stores locked away, the materials for energy and repair are taken from the blood stream. As long as insulin is present, the more the energy in the adipose tissue is locked away. As the glucose is removed from the blood stream hunger is initiated to maintain blood sugar levels within the correct homeostatic variables, and so you are physiologically and psychologically driven to eat.
When you eat the glucose, amino acids and fats enter your blood stream. The body is in storing mode as further insulin is released. The energy and materials from the food replenishes the energy stores in the muscles. Adipose tissue is still (generalisation) not touched.
Many people take a ‘pre-workout shake’ or have a pre-workout meal. The energy and rebuilding materials are already in your blood stream and therefore will be removed for storage by insulin. This will impinge upon workout performance as your body will be attempting to be catabolic and anabolic at the same time. Adipose tissue would be further restricted from releasing fat.
KEY POINTS: Very little fat from adipose tissue is used in restoring the energy in the muscles. This ‘fat burning’ is further inhibited by pre and post workout feeding. The adipose tissue fat stores are, as a gross generalisation, untouched.
However, it isn’t all bad news! During energy restricted diets weight training maintains muscle mass, and it is also possible to increase muscle mass while on energy restricted diet. Weight training carried out appropriately improves strength, balance, posture, proprioception, posture and mobility. In short weight training can seriously help your overall health and well-being.
It gets better still. Whilst in isolation weight training is not efficient at fat loss, it does release some nifty little hormones. These include testosterone, cortisol and adrenaline just for starters. During exercise insulin is suppressed (unless you have had a pre-workout feed that is). With insulin suppressed the triglycerides can be released from adipose tissue. The testosterone, cortisol and adrenaline are potent free fatty acid releasers and help release stores from adipose tissues.
With these free fatty acids being released they have to go somewhere. A negligible amount is utilised by weight training. So if we leave it there, following training the free fatty acids are reabsorbed by the adipose tissue. Steady state cardio uses mainly type I muscle fibres that utilise fat as an energy source, with moderate intensity engaging the type IIa muscle fibres too which also burn a considerable amount of fat as an energy source. So by doing cardio after weight training you are really starting to set yourself up as a potent fat burning machine!
My recommendation is that everyone should do weight (or at least resistance training) of some kind, unless they receive physical activity during the day that provides the same physical work. Human bodies are designed to move. If we don’t use it, we lose it. Weight training therefore has massive positive benefits for health and I advise everyone to do it. Just don’t expect it to be effective at targeting fat loss.
KEY POINTS: Weight training maintains or even increases muscle mass during energy restricted diets. It provides massive health benefits and is a recommended activity. It can assist in the fat burning process if carried out prior to doing steady state cardio work.
In summary weight training will be of a massive benefit to absolutely everyone. Yet, in itself, it is no good for burning ‘fat’. Used as part of a broader approach to fat loss, weight training is of massive benefit and is highly recommended. When looking to understand anything to do with the operations of the body it is important to look at the body from the smallest component parts, even down to the sub-atomic particle level, before building up to look at the body from a holistic whole. If we look at just component parts, or indeed just the ‘real world’ complete whole, we aren’t taking in the correct picture. Viewing it from the perspective of component details and holistic whole weight training is not effective, in itself, for fat loss.
I've been asked about the two studies that started me thinking. They were found in The Textbook of Obesity, Akabas, Lederman and Moore (brilliant book, highly recommended) and were studies in respect to weight training and obese people. They aren't definitive in themselves, yet, that's what got me thinking and asking the questions...that has led to this post and more. Just reading the extract should raise thoughts in so many areas for you.
Here is the particular extract and references:
Physical activity in the form of resistance training (e.g. weight lifting) also has been considered in the context of weight loss and weight loss maintenance. In theory, the acumulation of fat-free mass (i.e., muscle) through resistance training would result in weight loss by increasing resting metabolic rate. However, in practice this may not be the case. Resistance training does preserve lean muscle mass among individuals on low-calorie diets, but it does not appear that resistance training maintains or increases resting metabolic rate among dieters (32,33). These findings, however, do not negate the importance of the resistance training in the context of overall health. Preserving or increasing lean muscle mass increases overall body strength, which may increase the likelihood of sustained cardiovascular physical activity. This in turn may result in increased energy expenditure leading to weight loss or weight loss maintenance. Resistance training also may prevent loss of bone density associated with normal aging or calorie-deficit-induced weight loss.
PG 347, Textbook of Obesity.
32 Geliebeter A, Maher MM et al. Effects of strength or aerobic training on body composition, resting metabolic rate, and peak oxygen consumption in obese dieting subjects, Am J Clin Nutr 1997; 66; 557-63
33 Hunter GR, Bryan DR et al. Resistance training and intra-abdominal adipose tissue in older men and women. Med Sci Sports Exerc 2002; 34: 1023-8