Articles Tagged with: scientific evidence
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Exercise for weight loss – is this the best strategy?

Scientific observations across many years, thousands of individuals engaging in regular exercise, and a European fitness industry worth more than €26 billion serve as a clear indicator of the great benefits that being active can do for the human body. However, we must be honest about the fact that exercise for weight loss is not the cure-all panacea that it is often portrayed to be.

The elephant in the fitness room

Perhaps the biggest ‘elephant in the room’ in relation to exercise and fitness is its impact upon body fat storage! Exercise interventions for burning up body fat are often promoted as the answer in almost every magazine, blog and exercise video. It is even a major component of many government strategies for overcoming obesity and the world’s ballooning waistlines. It seems that no matter what, exercise attracts all the attention when it comes to answers for weight loss. There is plenty of ongoing debate over dietary factors in terms of how they impact weight loss, but exercise appears to rarely get questioned?

One of the aspects of weight loss that muddies the waters is that most people do not apply a single change when they try to lose weight and lower their body fat. Weight management usually results from a series of combined changes to an individual’s daily practices. There are many different strategies in the scientific literature that could be applied alongside exercise to help achieve weight loss such as:

  • A low calorie, low fat, or low carbohydrate diet
  • Increasing protein in the diet
  • A high fibre diet
  • Reducing sugar intake
  • Removing processed food
  • Improving sleep
  • Reducing stress and increasing relaxation
  • Detoxification protocols
  • Increasing activities of daily living
  • Using weight management supplementation
  • Lifestyle behaviour changes
  • Increasing public/group accountability
  • Alcohol reduction etc. etc. etc.
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It is rare that purely exercise, with no other associated change in behaviour, is the strategy of choice to drive a decrease in body fat. Perhaps that is a good thing too! The scientific evidence does not indicate that exercise alone is an effective option.

Exercise for weight loss evidence

If you put aside all other ways and focus upon exercise alone as the sole strategy for reducing body weight, it is lacking in punch. Don’t get me wrong it does have a positive effect, but the effect is fairly small! Certainly, nothing like what is proposed across the internet or modern social media channels. In 2006 an independent group of scientists representing the renowned Cochrane Collaboration published a meta-analysis (Shaw 2006) that looked at this very issue…by asking the question, ‘how effective is exercise for managing overweight and obesity?’ The research reviewed studies that only utilised the gold scientific standard of randomised controlled trials (RCT). These RCT’s looked at time periods between 3 to 12 months in duration comparing different bodyweight control methodology. Here are the facts which summarise their scientific findings on the matter up to 2005:

  • General exercise as a lone strategy provided weight loss between 0.5 – 4.0 kg
  • Low-intensity exercise as a lone strategy provided weight loss between 0.0 – 6.3 kg
  • High-intensity exercise as a lone strategy provided weight loss between 1.3 – 8.9 kg
  • Applying diet as a lone strategy provided weight loss between 2.8 – 13.6 kg
  • When diet was combined with exercise it provided weight loss between 3.4 – 17.4 kg
  • Diet combined with high-intensity exercise provided weight loss between 6.4 – 19.6 kg

Out of the 6 different strategy options looked at above, it is clear that a general exercise programme is the least effective of all the methods applied. High-intensity exercise as a lone strategy does improve things and appears to be about twice as effective as general exercise. However, all three lone exercise strategies fall short of lone dietary or combined exercise and dietary strategies. The authors of this study provided some very good summary statements which help to bring in a few other considerations than just the factual weight loss ranges shown above:

  • These findings are consistent with previous reviews (Miller 1997;McTigue 2003Douketis 2005) that demonstrate only modest (less than five kg) weight loss with exercise alone as a weight loss intervention, and improved weight loss with diet and exercise compared with exercise alone.
  • The results of this study support the hypothesis that vigorous activity is more effective than moderate or light intensity exercise in stimulating weight loss…However, high-intensity exercise was only significantly better than low-intensity exercise at inducing weight loss when undertaken without dietary change. When diet was also modified, exercise intensity did not significantly increase the degree of weight loss.
  • Both low calorie and low-fat diets were used as comparison dietary interventions across clinical trials. Both were more effective at facilitating weight loss than exercise alone. This is consistent with the findings of other studies that also demonstrate dietary modification is superior to exercise in obtaining weight loss in overweight and obese adults (Curioni 2005Hansen 2005).

Exercise is beneficial

You may be thinking that exercise to drive weight management is not very helpful and that a diet alone would be best to lose weight? Well, there are other benefits that should not be overlooked in relation to applying exercise as part of a weight-loss strategy. These ‘additional’ benefits certainly warrant the inclusion of exercise in the battle of the bulge. The study authors state:

  • Positive effects on CVD risk factors were demonstrated with exercise interventions in overweight and obese adults in this study. Those who participated in exercise interventions alone reduced systolic and diastolic blood pressure, cholesterol, triglycerides and fasting serum glucose. They also increased HDL levels. The changes that were statistically significant compared with no treatment were changes in diastolic blood pressure, triglycerides, HDL and glucose… These changes were independent of significant weight loss. Weight loss does not appear to uniformly improve cardiovascular risk factors, particularly if 5% or less bodyweight reduction (Douketis 2005).
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Conclusion

In short, exercise imparts considerable benefits to the cardiovascular system that help reduce heart disease and diabetes risk, even in the face of minimal weight reduction. There are also many other benefits from exercise that would literally take a textbook to fully explain. We are not discounting exercise at all. But we need to be honest about its fat burning capacity as a sole strategy – it just is not that powerful! So the real take-home messages of this weight loss science blog are simply:

  1. Weight loss is best achieved through carefully planned dietary modification combined with the appropriate application of higher intensity exercise methods
  2. Exercise is very effective at reducing heart disease and metabolic health risk factors regardless of weight management and as such is a necessary part of a healthy lifestyle
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High-intensity Intermittent Training (HIIT) science – fact or fiction?

High-intensity training has been a hot media topic over the last couple of years, from magazine and newspaper articles to prime time television shows on the BBC. It seems that the idea of achieving as much benefit within less time is a solution that appeals to many people in a world where available workout time is at a premium. However, the idea of using higher intensity training to boost physical benefits is certainly not a new one. Early research by scientists like Bahr, Tremblay and Tabata, all of which have become renowned in this field, date back to the early 1990s. Take note that not everything published in the media or blogosphere on high-intensity training is justified by the scientific literature. Fitness professionals and enthusiasts often use the basic concept of high-intensity interval training and embellish the truth a little, perhaps unknowingly, to suit their own desired outcome. The intent in this post is to glean the facts around this popular training method from the scientific literature so that you are correctly informed going forward in your utilisation of HIIT as a training modality.

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  • Tremblay showed in 1994 that a 15 week HIIT programme reduced total skinfolds 14 mm subcutaneous body fat compared to a 20-week endurance training (ET) programme that only reduced by 4mm total skinfolds. The HIIT protocol being 3.5 times more effective.  The ET programme was steady-state exercise beginning at 30 minutes at 60% and progressing to 45 minutes at 85% HR max as the test subjects were able. The HIIT protocol was 30 minutes of short bursts, beginning at 10 x 15-second bursts progressing to 15 x 30-second bursts as the test subject was able.
  • In 1996 Tabata published a study demonstrating that 8 bouts of 20 seconds at 170% VO2max with 10 seconds rest in between each set had the same benefits to the aerobic system as 60 minutes of steady-state training at 70% VO2max. However, the HIIT protocol also caused a 28% improvement in anaerobic capacity that was not observed in the low-intensity protocol.
  • Borsheim and Bahr are renowned for their work on increased metabolism following exercise, also known as excess post-exercise oxygen consumption (EPOC). In 2003 they carried out a substantial review of the scientific literature and showed that exercise intensity has a curvilinear relationship with EPOC whereas exercise duration is linear. Increased EPOC for 8-12 hours after intense training periods was common.  In simple terms, you get more bang for your EPOC buck by driving CV intensity up rather than spending longer at moderate intensities.
  • Talanian in 2006 showed that a 2 week (7 sessions) aerobic HIIT training protocol (10 x 4 min, 90% bursts with 2 min rest periods) significantly (up 25%) increased muscle fatty acid oxidation.
  • Trapp in 2008 showed that HIIT training is effective even in overweight deconditioned women as well. A 20-minute cycling HIIT protocol was compared to a 40-minute steady-state cycling regime of the same frequency for 15 weeks. Both groups had similar CV improvements but the HIIT group had significantly greater body fat loss on legs and trunk and improvements in insulin resistance.
  • Boucher in 2010 reviewed the available scientific evidence surrounding HIIT and concluded that while there was valid evidence to show it is more effective at decreasing both subcutaneous and abdominal body fat compared to steady-state training, there is also clear evidence of individual variation in response – not all participants appear to receive the same level of fat loss benefit.
  • Resistance training has also been shown in scientific studies (Melby 1993, Laforgia 1997) to influence EPOC and fat burning when lower volume, higher intensity weight training is utilised in preference to higher volume, moderate resistance work, but the research is still ongoing in this field.

While this is just a brief look at some of the science on high-intensity training, it does illustrate that in comparison to steady-state exercise, the benefits of HIIT training are:

  • it may be as good at providing aerobic training benefits
  • it is better a stimulating anaerobic training benefits
  • it significantly improves body fat reduction
  • it increases EPOC for up to 12 hours’ post-training
  • it improves insulin sensitivity to working muscles

It is important to note that the majority of these studies have been performed in a highly controlled environment and most often using a cycle ergometer (bike) or a treadmill. Whilst it is reasonable to assume these benefits may also carry over to other training modalities, such as circuits, group training or resistance work there is much less current evidence to suggest this is true. Perhaps in time the science will more fully support and provide confirmation that high-intensity training has a broader application across a range of training modalities with the same beneficial results.

In the meantime, while we wait for science to catch up, it is clear that the many different methods of HIIT training can be great fun, they definitely save on time in the gym and it can deliver a real motivational boost to your training. If it does provide an increased fat burning boost as well, then all the better!

Do you love fitness? Ever thought about making a career out of your passion? Find out more about how you can do that through the Nordic Personal Trainer Certificate from Nordic Fitness education. 

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