While diet has a stronger effect on weight loss than physical activity does, physical activity, including exercise, has a stronger effect in preventing weight gain and maintaining weight loss. Moderate aerobic exercise includes such activities as brisk walking, swimming and mowing the lawn. Share Tweet Pin PrintQuite apart from the aesthetics of a slim toned body, for most sportsmen and women, lower levels of body fat equate to better performance.
Although increased fat burning has bene?cial implications for sport performance, many people who exercise regularly do so for general ?tness, health and aesthetic reasons rather than to increase fat burning per se.
Any exercise programme that promotes increased fat burning therefore can help you to reach and maintain your target body weight more easily, bringing you all the associated health and kudos bene?ts sooner rather than later. Before we get into the nitty-gritty of maximising fat burning, it’s important to understand that the fundamental laws of chemistry and physics still apply (see box 1) and there’s absolutely no way of circumventing them. There’s an unlimited supply in the air around you and even a lean body contains a very large amount of stored chemical energy in the form of body fat. Unlike carbohydrate (the other main fuel for the body), fat needs an abundant supply of oxygen in order to be converted to energy. Very high-intensity exercise like sprinting or lifting weights (resistance training) uses different metabolic pathways to produce energy, most of which comes from carbohydrate burning. One of the most powerful ways to manipulate the proportion of fat used to produce energy is to adjust the intensity of your 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. 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. Increased resting metabolic rate – as mentioned earlier, some resistance training can be a very useful adjunct to an aerobic training programme for fat loss. 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). 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.
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.
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. 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 ?tness 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). However, there is evidence to suggest that fewer but longer sessions (?tness permitting) may be advantageous to burn fat because we know that fat oxidation becomes an increasingly important fuel as the duration of exercise increases (4). 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. Finally, and as previously mentioned, any fat burning programme should ideally include some resistance training for all the reasons given earlier. When building up your total weekly volume, you need to ensure you do so only gradually to avoid the risk of injury or burnout.
For many people, lifestyle factors such as work and family dictate what time of day they will train! 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 ?nal 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 (8). An initial weight loss consisting of muscle can be comforting, but the bathroom scale belies the truth.
This type of exercise is based on several different dance routines and works the entire body. So if you cut 500 calories from your diet each day, you’d lose about 1 pound a week (500 calories x 7 days = 3,500 calories). Get at least 150 minutes a week of moderate aerobic activity or 75 minutes a week of vigorous aerobic activity. This chart shows the estimated number of calories burned while doing various exercises for one hour. So if you wander into almost any gym and ask people why they train or what spurred them to begin training, it’s hardly surprising that weight loss comes right at the top of the list! Together, these facts explain why there’s such an interest in fat burning and how to maximise it during exercise.
If you want to lose weight, you have to create a ‘negative energy balance’ in your body – ie expend more calories than you consume.
Provided your exercise intensity isn’t too severe (ie you have enough oxygen ?owing around your body), you can derive a large proportion of energy throughout this aerobic exercise from fat.
This is why it’s not an effective way to burn fat, although some resistance training can enhance a weight loss programme by helping to sustain or increase muscle mass (see later). Each pound of body fat contains approximately 3500kcals of energy, so to lose a pound of body fat over any given time period, you have to burn 3500kcals more energy than is contained in the food and drink you consume. The question that follows therefore is how hard should your aerobic training be to maximise fat burning? You can see that that as the exercise intensity (in watts) increases, the rate of fat burning increases, reaching a maximum of around 35 grams per hour at 180 watts.
But now suppose you exercise at 75% MHR for an hour and burn 700 calories (because you’re working harder). Even more importantly, by increasing your oxygen processing capacity, your muscle cells will become more ef?cient at using fat for energy, even at higher intensities. This is because very high intensity exercise such as resistance training increases muscle mass, which is a very desirable thing. 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 ?gure 2). Moreover, this intensity is usually identi?able because at this point, many people will perceive a signi?cant step up in their rate of exertion. 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, in the example above, three sessions of 60 minutes may be preferable to six sessions of 30 minutes. Unless you’re already an experienced trainer, it’s strongly recommended that you seek advice from a ?tness professional before putting together any programme. 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).
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!
Clearly a better more long term strategy is required to cause sustainable and permanent weight loss. This means abandoning refined grains and sugar, processed oils and trans fats, food ingredients and sweeteners, and replacing them with whole grains, vegetables, quality protein and healthy fats. They followed 124 patients and collected there BMI and type of exercise every 6, 12, 24 and 36 months.
Because of changes that occur in the body over time, however, calories may need to be decreased further to continue weight loss. However, to effectively lose or maintain weight, some people may need up to 300 minutes a week of moderate physical activity. No specific amount of time for each strength training session is included in the guidelines. Strength training can include use of weight machines, or activities such as rock climbing or heavy gardening. Specific calorie expenditures vary widely depending on the exercise, intensity level and your individual situation. However, by enhancing fat burning, you increase the proportion of your expended calories that will come from stored body fat.
As we’ve hinted above, lower intensities favour fat burning but as the intensity increases, carbohydrate becomes more and more important until at very high intensities, almost all of the energy to fuel exercise comes from carbohydrate burning and none from fat-burning.
Above 180 watts, the amount of fat burned drops off rapidly so that by 300 watts, it’s contributing virtually nothing.
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’.
Another important point to emphasise is that your ?tness level will have a big impact on the exercise intensity at which you reach Fatmax. This is not surprising really as we know that regular aerobic training ‘teaches’ the body to burn fat more ef?ciently. 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). Another bene?t of structuring sessions this way is that it allows longer periods of recovery in between each bout of exercise. For the same workload therefore, these ?bres have to contract more intensely and as we have seen, at high muscular intensities, carbohydrate burning becomes much more dominant. The most obvious way to take advantage of this effect is to train ?rst 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).
However, the quality of weight loss is poor because a large amount of the weight is muscle. Whatever the reason, most individuals who begin a diet are initially rewarded with weight loss and this can continue for a number of weeks or even months. In this regard the old paradigm of calorie counting and aerobic exercise must be discarded and a new paradigm accepted in its place. Traditional diets are high quality diets and they cause weight loss without the need for calorie counting or exercise.
A second important fact that needs to be born in mind is that all of us, all of the time, are burning all three types of food calories (fat, carbohydrate and protein) to produce energy. Carbohydrate burning increases steadily too but at around 180 watts (just as fat burning drops off) it jumps dramatically so that by 300 watts, it’s contributing 100% of the energy for exercise.
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 balance).
For example, a ?t runner who can sustain 16kmh (10mph) can easily burn 1000kcals in an hour. 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 signi?cantly, helping you to achieve your negative energy balance more easily. The goal is to increase your total volume so that you burn more fat calories (but see box ‘Safety ?rst!’).
However, eventually, the increased appetite and reduced metabolic rate causes them to regain all the lost weight, and usually some more on top. Thoughts should turn instead to diet quality, rather than diet quantity, with resistance training replacing aerobic style exercises.
By swapping to traditional eating plans, long term successful weight loss is far more likely. The guidelines suggest that you spread out this exercise during the course of a week, and sessions of activity should be at least 10 minutes in duration. The contribution from protein is minimal except when vigorous exercise is performed in the absence of carbohydrate (a subject we’ll discuss in part II of this article) so in actual fact, most of your energy is derived from carbohydrate and fat. 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.
The best way to maximise lean muscle mass is to add one or two sessions of resistance training into your weekly aerobic exercise program. The cool-down session should last a similar amount of time as the warm-up, with the pace gradually decreasing. It follows therefore that increasing the proportion of your expended energy from fat is associated with a reduced proportion from carbohydrate and vice-versa. The combination of a low resting metabolic rate and a stimulated appetite significantly increases the risk of weight regain at a future time point. Stretching exercises would be appropriate after aerobic exercise.Start you aerobic program by doing 20 minutes of brisk walking per session.
This kind of intensity presents little challenge to the aerobic system, so there’ll be relatively little improvement in aerobic ?tness. 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.
Increase slowly the time of your workout and then your intensity.Chief NutritionistSince 2005, Dr.
As the proportion of carbohydrate burning increases, fat burning decreases; as the proportion that you burn fat increases, the carbohydrate contribution decreases.
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.
Miranda has served at the Obesity Control Center® as Chief Nutritionist with bariatric surgery patients.Dr. Miranda graduated from medical school in 2000 but with a growing concern for nutrition and its profound impact on the lives of patients, she furthered her education and received a Diploma of Nutrition in 2004, followed by a Masters degree in that field of study. That’s because during aerobic type exercise, energy is provided by combining carbohydrate, fat and (to a small extent) protein calories with oxygen.
She has also taught Anatomy and Chemistry and has practiced as a general physician and cosmetologist. Miranda currently practices at Excel Hospital where she specializes in working with overweight children, diabetic patients and speaking at conferences to senior executives on the importance of nutrition and health.
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