Strength and Fitness - The Impartial Guide to strength, fitness, endurance and nutrition

Exercise For Weight Loss

Whilst dieting can be an important tool in the fight against obesity, most diets are not effective in the long run. Current research suggests that the obesity epidemic that is affecting western world countries is more to do with a reduction in physical activity levels rather than excessive consumption of food. If you take the case of the united states, the calorie intake amongst adolescents has remained fairly static over the last 2-3 decades yet the rates of obesity have increased by around 10% in this group. Over the same time the rates of physical activity amongst this group has decreased significantly (~10%). Therefore it appears that the increased rates of obesity may be more linked to reduced levels of physical activity rather than changes in calorie intake.

Exercise treats the cause of weight gain rather than the symptoms

Whilst dieting may provide a short term means of managing/reducing weight it is actually treating the symptoms of the problem (the weight gain) rather than the actual cause of the problem (reduced physical activity). Since most diets are unsuccessful in the long run (when viewed over a period of years) a more effective approach is to make changes to lifestyle so that there are increased levels of physical activity, or a combination of dietary changes and increased physical activity. 

The benefits of exercise for weight loss

One of the big advantages of exercise is that not only do you burn more calories during the exercise itself but your metabolic rate is increased for several hours after completion of exercise - post exercise energy expenditure. This means that even after exercise is completed your body will continue to burn additional calories for up to a 24-hour period after exercise. The increases in post exercise energy expenditure appear to be greater following more intense exercise.

An exercise programme will also lead to small increases in lean muscle mass. Any increase in muscle mass is known to have positive effects on metabolism which will increase daily energy expenditure and further increase weight loss. Whilst small increases in lean muscle mass can occur following aerobic exercise greater gains can be achieved by including a few resistance exercises into any training plan.  Therefore, as part of an exercise programme for weight loss you should also include a few resistance exercise, in addition to cardiovascular exercise, in order to increase lean muscle and therefore speed metabolism. If you are concerned about putting on weight through doing resistance exercise it is important to remember that including a few light weights will not lead to huge amounts of muscle gain but will increase the amount of energy burned during the exercise routine, increase metabolism and enhance fat loss.

How much exercise for weight loss

You should look to exercise for at least three days a week (research suggests that around 5 days a week is probably the optimum number) and should aim to burn around 300-500 calories (ideally 500 but the more the better) during each workout. The primary exercise should be cardiovascular (CV) exercise such as walking, jogging, cycling, swimming etc. If you are exercising in the gym then you will have access to a number of different machines including treadmills, cross trainers, upright bikes, recumbent bikes, steppers, rowers, elliptical trainers. Using gym machines can be beneficial in that you can monitor your exercise level and they will give you an estimate of calories burned during the exercise.

Aim to include resistance training on 2-3 days a week to slightly increase lean mass. If you are concerned about putting on too much muscle only use light weights that you can comfortably complete 15 repetitions - you should be able to complete the 15th repetition feeling like you could still do a few more. Aim to complete 2-3 sets per muscle group. If you are limited for time you may find it easier to spread the exercises over 2-3 workouts (e.g. day 1 do upper body exercises, day 2 do leg exercises)

Exercise intensity and weight loss

Another consideration is the exercise intensity if you have the time and motivation to do a longer workout (around 60 mins of CV) then keep the level fairly moderate around 70% of maximum effort (70% of maximum heart rate**)  – most cardio machines now have a built in heart rate monitor, alternatively you may wish to purchase your own heart rate monitor. If you only have time to do a shorter work out then aim to exercise at a slightly higher intensity (e.g. ~ 80% of maximum HR). By training at a slightly higher level you will burn more calories during the workout and will raise your metabolic rate to a higher level after exercise so that you burn more calories during the post exercise period.

Additional considerations with exercise for weight loss

The time of the day that you exercise can have an effect on exercise. Whilst it doesn't appear that training at a specific time of day significantly enhances the amount of calories consumed during exercise you may find it easier to exercise at a specific time of day. This is largely determined by your bodies circadian rhythm - basically your bodies natural body clock which determines what your heart rate, blood pressure, body temperature and hormone levels are at different times of the day. For most people the time that they exercise is largely determined by the constrainsts of work, family life etc. However, if you are lucky enough to train at different times of the day you may find that you are more motivated and better able to train at a specific time of the day - for most people this is generally late afternoon/early evening. This can vary depending on your lifestyle - e.g. if you have worked nights for many years your body clock will be different and you may find that you train better in the mornings after work.

If you are combining aerobic exercise with dieting it is important that you consume enough calories, in the form of carbohydrate and protein, to ensure that your muscle recover adequately from exercise and that you do not start to deplete your muscles of muscle glycogen. When muscle glycogen levels become depleted it can lead to you feeling low on energy and may increase muscle breakdown which is counterproductive to both dieting and exercise. To protect against this you should ensure that you consume some carbohydrates within 60 minutes of completing exercise - this is best done by timing meals around exercise (e.g. if you train in the evening don't consume your afternon meal until after exercise). If you are training early in the morning you may find it better to have breakfast after exercise - this may help to increase fat metabolism when exercising (consuming carbohydrate prior to exercise would mean that you are burning off the carbohydrate you have just eaten and would lead to a decreased consumption of fat reserves during that workout). This will also ensure that you are supplying your muscles with the carbohydrates just when it needs them (after exercise).  

By combining a structured exercise programme with a healthy eating program you will see the best results.

** You can estimate 70% of your maximum heart rate using the heart rate training zone table in the exercise for health section

Exercise for weight loss summary:

  • Increased levels of obesity appear to be more linked to reduced physical activity than increased calorie consumption.
  • Whilst dieting treats the symptoms of weight gain exercise actually helps to treat the cause of weight gain
  • Most diets appear to be unsuccessful in the long run
  • Exercise significantly increases energy expenditure during the exercise as well as after the completion of the exercise
  • The small increases in lean muscle mass, following exercise, can enhance metabolism and weight loss
  • Resistance training can be used to further increase gains in lean muscle mass
  • Aim to complete 3-5 exercise sessions/week in which you burn 300-500 calories
  • Sessions should consist primarily of aerobic exercise (30-60 minutes a session at 70-80% of maximum heart rate) - walking, jogging, cycling, swimming etc - but you may wish to include resistance exercises on 2-3 days/week
  • By combining a structured exercise programme with a healthy eating program you will see the best results.