Classification: UNCLASSIFIED

DON’T RULE OUT HIGH INTENSITY EXERCISE!You might think that exercising exactly at your Fatmax intensity is the best way to lose body fat but this may not necessarily be the case. There are a number of reasons for this:Larger total calorie burn – suppose you exercise at 60% of your maximum heart rate (MHR) for an hour, burn 500 calories and 50% of those come from fat then you’ll have burnt 250 fat calories. But now suppose you exercise at 75%MHR for an hour and burn 700 calories (because you’re working harder). Even if only 33% of your energy comes from fat, you’ll still have burnt 230 fat calories but in total, you’ve also burnt an extra 200 calories from other fuels (mostly carbohydrate). This means that you’ll have an extra 200 calories to play with in terms of food intake and still stay the right side of the thermodynamic equation for the day (remember, you have to create a negative energy balanceIncreased fitness and fat burning – training at a higher % of your MHR will progressively increase your aerobic fitness; in very simple terms, as time goes by you’ll be able to train harder and burn more calories per hour for less perceived effort. Even more importantly, by increasing your oxygen processing capacity, your muscle cells will become more efficient at using fat for energy, even at higher intensities. This explains why someone who is fit finds it relatively easy to stay leanFor example, a fit runner who can sustain 16kmh (10mph) can easily burn 1000kcals in an hour. If they can do that while working at say 75% of MHR, they’ll probably derive something in the region of 400-500kcals from fat. But suppose you’re only ever used to working at 60% MHR. This kind of intensity presents little challenge to the aerobic system, so there’ll be relatively little improvement in aerobic fitness. With a total calorie burn of around 400-500 per hour and a maximum of around 50% from fat, it’s unlikely you would burn more than 200 fat calories in an hour. Of course, you could achieve the same fat calorie burn as our fi t runner by doubling the length of your workout, but quite apart from the boredom, most people simply don’t have time for 2-hour workouts, and you still wouldn’t be improving aerobic fitness at these lower intensities.Increased resting metabolic rate – as mentioned earlier, some resistance training can be a very useful adjunct to an aerobic training programme for fat loss. This is because very high intensity exercise such as resistance training increases muscle mass, which is a very desirable thing. Kilo for kilo, muscle mass is metabolically far more active than adipose (fat) tissue. Increasing your muscle mass with the addition of some resistance training means that the rate at which you burn up energy even while resting can be boosted significantly, helping you to achieve your negative energy balance more easilyThe best way to maximise lean muscle mass is to add one or two sessions of resistance training into your weekly aerobic exercise program. You don’t need to spend hours at the gym either; very significant benefits can be had by as little as two 30-minute resistance sessions per week. Sessions comprising of 10-12 exercises designed to work all the major muscle groups (one to two sets of 10-15 repetitions per exercise with enough weight set so that the repetitions can only just be completed) will produce good results in those who are not experienced resistance trainers.
FATMAX
Although several studies have looked at the relationship between exercise intensity and fat oxidation at a particular intensity, it was only recently that this relationship has been studied over a wide range of exercise intensities (2). In general terms, what happens is that carbohydrate oxidation increases proportionally with exercise intensity, whereas the rate of fat oxidation initially increases but decreases again at higher exercise intensities (see figure 2). The point at which fat burning reaches its peak is known as ‘Fatmax’ and the range of exercise intensities close to Fatmax is sometimes referred to as the ‘Fatzone’.

It’s often claimed that you have to exercise at low intensities to burn fat, but you can see from the graph this is not necessarily true. The right hand side of the grey Fatzone is quite vigorous but still close to Fatmax. Another importantpoint to emphasise is that your fi tness level will have a big impact on the exercise intensity at which you reach Fatmax.

In a series of studies conducted by Professor Jeukendrup and his team of researchers at the University of Birmingham, it was found that for trained subjects, exercising at a moderate intensity (62-63% of VO2max or 70-75% of maximum heart rate [also known as HRmax]) was the optimal intensity for fat oxidation. However, for less trained individuals, Fatmax occurred at just 50% of VO2max(2,3). This is not surprising really as we know that regular aerobic training ‘teaches’ the body to burn fat more efficiently.

In reality, the exact intensity at which fat oxidation peaks is less important because within 5-10% of this intensity (or 10-15 beats per minute), fat oxidation will be similarly high (ie in the Fatzone), and only when the intensity becomes dramatically higher will fat oxidation will drop rapidly. Moreover, this intensity is usually identifiable because at this point, many people will perceive a significant step up in their rate of exertion.

EXERCISE RECOMMENDATIONS
Taken as a whole, the evidence suggests that for maximum fat burning during exercise itself, you should exercise aerobically at the higher end of your Fatzone, which depending on your fitness will be around 60-80% of your maximum heart rate (NB your maximum heart rate is roughly given as: 220 minus your age in years). As for duration and frequency of exercise sessions, the most important factor is your total energy expenditure over any given time period. So for example, six aerobic training sessions per week of 30 minutes’ duration at say, 70%MHR would be equivalent to three sessions of 60 minutes at the same %MHR (180 minutes in total). The goal is to increase your total volume so that you burn more fat calories (but see box ‘Safety first!’).

However, there is evidence to suggest that fewer but longer sessions (fitness permitting) may be advantageous for fat burning because we know that fat oxidation becomes an increasingly important fuel as the duration of exercise increases (4). So for example, in the example above, three sessions of 60 minutes may be preferable to six sessions of 30 minutes. Another benefit of structuring sessions this way is that it allows longer periods of recovery in between each bout of exercise.

Another caveat worth adding is that the type of aerobic exercise undertaken may impact the amount of fat burning even when the exercise intensity is identical. For example, fat oxidation has been shown to be higher for a given oxygen uptake during walking and running compared with cycling (5). The reason for this is not well understood, but some researchers believe that it is related to the greater power output per muscle fibre in cycling compared to running. Compared to running, the work done during cycling is concentrated in fewer muscle fibres because fewer muscles in total are involved in the cycling action. For the same workload therefore, these fibres have to contract more intensely and as we have seen, at high muscular intensities, carbohydrate burning becomes much more dominant.

Finally, and as previously mentioned, any fat burning programme should ideally include some resistance training for all the reasons given earlier.

SAFETY FIRST!When building up your total weekly volume, you need to ensure you do so only gradually to avoid the risk of injury or burnout. Unless you’re already an experienced trainer, it’s strongly recommended that you seek advice from a fitness professional before putting together any programme. This will help ensure you derive maximum benefits as safely and comfortably as possible.

EXERCISE TIMING
For many people, lifestyle factors such as work and family dictate what time of day they will train! However, if you have a choice, some evidence suggests that the longer the period between your last meal and your exercise session, the greater the proportion of energy that will be derived from fat (6). The most obvious way to take advantage of this effect is to train first thing in the morning before breakfast and indeed, research has shown that the total fat oxidised during exercise (and for two hours after exercise) is greatest when morning exercise is performed in the fasted state (ie before breakfast) (7).

It’s important to stress however that this approach becomes less appropriate for longer duration sessions (over one hour) where ‘training on empty’ could result in excessive fatigue as a result of low blood sugar and stored muscle carbohydrate (glycogen). A final recommendation that follows from the studies above is that where fat burning is the number one goal (rather than performance), consuming a carbohydrate drink before or during training is not recommended because it reduces the proportion of energy derived from fat during subsequent exercise (. More generally, your nutrition before, during and after exercise will play a powerful part in determining how much fat you’ll burn but that’s a whole different topic and one we’ll consider in part II of this series!

About Andrew Hamilton
Andrew Hamilton BSc Hons MRSC ACSM is the commissioning editor of, and sports nutrition writer for, ‘Peak Performance’, the worldwide leading research publication for athletes and coaches. He is also commissioning editor of and contributor for ‘Sport Injury Bulletin’, providing the very latest sports injury advances into practical advice on prevention, treatment and rehabilitation.
Andrew also writes for a number of other publications, including ’Cycling Weekly’, ’220 Triathlon’, ’The British Journal of Cycle Coaching’, ’Athletics Weekly’, and ’Workout Magazine’.


REFERENCES
1. Data from Bradley J, University of Central Lancashire, 2002
2. Int J Sports Med 24: 603-608, 2003.
3. Int J Sports Med 26 Suppl 1: S28-37, 2005.
4. Obesity (Silver Spring). 2007 Sep;15(9):2256-62
5. Metabolism 52: 747-752, 2003
6. Int J Obes (Lond). 2005 Aug;29(:966-74
7. Appl Physiol Nutr Metab. 2006 Oct;31(5):502-11
8. J Sports Sci. 2003 Dec;21(12):1017-

A lot of english. U could have stated a few routines and endurance exercises we could do.