The calming effect of the kick: Can martial arts be used as an aggression-reduction intervention for young people?

In a word: Yes!


The Evidence

Harwood, A., Lavidor, M., & Rassovsky, Y. (2017). Reducing aggression with martial arts: A meta-analysis of child and youth studies. Aggression and Violent Behavior, 34, 96-101. http://dx.doi.org/10.1016/j.avb.2017.03.001


What did the meta-analysis look into?

This meta-analysis investigated whether traditional martial arts classes (karate, aikido, judo, taekwondo, and kempo) have the potential to reduce aggression in young people, aged 6 to 18. The classes took place at schools, hospitals, martial arts clubs, or youth centres, with an intensity that ranged between two and a half weeks training (daily), and 10 months of training (3 times per week). Before the martial arts training, the young martial artists exhibited various forms of verbal and physical aggression, spanning from disobedience and defiance, to more serious delinquent activities that resulted into arrest and incarceration. The meta-analysis synthesized evidence from 12 studies (4 of which were experimental), including 507 young people from Italy, India, Canada and the USA.


Did the evidence suggest that martial arts classes reduced aggression?

Yes! The meta-analysis found that martial arts training reduced aggressive behaviours across all young populations. This was regardless of the particular martial art, the duration of the training, and the location of the practice. Predictably, the longest training (10 months) reduced aggression the most.


The take-home message

Traditional martial arts can reduce verbal and physical aggression in young people. The type of martial art does not seem to matter but the longer it is practiced, the greater the calming effect. The mechanisms thought to reduce aggression are the same across traditional martial arts and include repetitive movements, continued eye contact with the “opponent”, controlled behaviours, and a requirement for compliance and respect to the teacher and class.

Updated: Apr 18, 2018



The Evidence:

Harris, L., Hamilton, S., Azevedo, L. B., Olajide, J., De Brún, C., Waller, G., ... & Ells, L. (2018). Intermittent fasting interventions for treatment of overweight and obesity in adults: A systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports, 16, 507-547. doi: 10.11124/JBISRIR-2016-003248


What did the meta-analysis look into?

This meta-analysis investigated whether intermittent fasting (IF) programmes, also known as intermittent energy restriction programmes, can effectively treat overweight and obesity. The meta-analysis synthesized evidence from 6 experimental studies, including 400 overweight to obese adults from the USA and the UK. The weight loss of the people who fasted was compared to the weight loss of those who were on ‘usual diets’ (i.e., counting & reducing calories), or to the weight loss of people who were on no diet whatsoever. The IF programmes lasted between 3-12 months and varied in nature (e.g., alternate day fasting, fasting for two days, and up to four days per week). All IF programmes allowed people to consume ≤800 calories on at least one day per week, but on no more than six days per week. The meta-analysis primarily focussed on weight loss, and, when enough data were available, provided measures of body fat; waistline circumference; and cardio-metabolic outcomes (cholesterol, triglycerides, glucose, insulin, satiety hormones, and inflammation). People who exercised were not included in the study.


What did the evidence suggest for weight loss and cardio-metabolic outcomes?


IF versus dieting (i.e., counting & reducing calories):

IF and dieting resulted in similar weight loss (minus 1 kilo on average), but IF resulted in greater fat loss (minus 1.38 kilos on average) and greater waistline circumference reduction (minus 2.14 centimetres on average). Fasting improved insulin levels more, but other cardio-metabolic outcomes were similar.


IF versus no diet (i.e., eating freely):

Compared to no diet, IF resulted in more weight loss (minus 4.14 kilos on average) and more fat loss (minus 3.24 kilos on average). Data were not enough to provide information for other outcomes.


The take-home message

Intermittent fasting appears to be as effective as dieting (i.e., calorie restriction) when it comes to achieving weight loss, but more effective when it comes to minimizing fat, waistline circumference, and insulin concentrations in the blood. Also, IF appears to be more effective than ‘eating freely’ when it comes to weight and fat loss. Notably, all types of IF programmes appeared to be equally effective in achieving these outcomes. Broadly speaking, IF seems to be a successful strategy for the treatment of overweight and obesity, but this is based on data from 400 people, only. More studies, confirming these results, are required before the (routine) use of IF can be recommended.

Updated: Apr 18, 2018

The Evidence:

Thorogood, A., Mottillo, S., Shimony, A., Filion, K. B., Joseph, L., Genest, J., ... & Eisenberg, M. J. (2011). Isolated aerobic exercise and weight loss: A systematic review and meta-analysis of randomized controlled trials. The American Journal of Medicine, 124, 747-755. doi:10.1016/j.amjmed.2011.02.037

What did the meta-analysis look into?

This meta-analysis investigated whether an isolated aerobic exercise programme of at least 2 hours per week can result in noteworthy weight loss. Isolated exercise programmes measure the effects of exercise alone – without dieting. The intensity of exercise programmes reviewed was moderate (raised heart rate up to 40 to 80 percent higher than when sitting) and included walking, jogging, cycling & rowing machines, aerobic routines, and mini-trampoline. The meta-analysis synthesized evidence from 14 experimental studies, including 1847 overweight and obese adults from Europe, North America, Japan, and Brazil. The weight loss of those who were on the 2-hour weekly exercise programme was compared to that of overweight & obese adults that did not follow any scheduled aerobic exercise.

In addition to weight loss, the meta-analysis also measured the effects of the 2-hour exercise programme on fat, blood pressure, cholesterol, and triglyceride levels.

What did the evidence suggest for weight loss and related outcomes?

In general, those who exercised lost more weight than those who did not, but the weight loss was negligible. Specifically, the 6-month exercise programmes resulted in losing 1.6 kilos, reducing the waistline by 2.12 cm, and in small reductions in total cholesterol and blood pressure. The 12-month exercise programmes resulted in losing 1.7 kilos and reducing the waistline by 1.95 centimetres. There were not enough studies to synthesize evidence for other outcomes, at 12 months.

The take-home message

Obese and overweight people that engage in exercise programmes of moderate intensity may experience weight loss (up to 1.7 kilos) and waistline reduction (up to 1.95 centimetres), assuming that the exercise is maintained for at least 2 hours per week, and over the period of a year. This type of exercise may also result in small improvements in cholesterol and blood pressure. However, these outcomes are too small to justify recommending stand-alone exercise programmes. Broadly speaking, exercise alone appears to be an ineffective weight loss strategy for obese and overweight people.