Running Endoprhins Ghrelin + Cortisol 
Weight training Insulin + Testosterone + GHNone 
WalkingCortisol None 
Kettlebell training Insulin + Testosterone + GHGhrelin + Cortisol 
Pilates/Yoga Cortisol + Insulin None 



Whilst running is a great from of exercise, if you run often and continually push hard, you run the threat of significantly increasing cortisol which is the bodies main stress hormone. If you’ve also lowered your caloric intake and are eating less carbohydrate, this could turn your body catabolic, which means your body starts to break down muscle tissue for energy, which is obviously really bad news as your muscle mass regulates your metabolism! Lose muscle and you’ve lowered your metabolic rate.

The other issue with running is that it can significantly raise ghrelin, which is a hunger hormone. So whilst you may burn a lot of energy on the run, this is often compensated for in a post run feast. However this seems to be an individual response and for some people it can have an appetite blunting affect.  

For these reasons I really don’t see running as a good option if fat loss is the main goal. You can do ‘some running’, but it shouldn’t be the main focus if fat loss is the goal. 

Weight training 

Lifting weights and building muscle mass raises some very helpful hormones in your body. Whilst it doesn’t raise insulin, this is mentioned because of the positive effect on insulin sensitivity. Insulin is a hormone that is released after eating carbohydrates, which in the blood then become known as glucose. Insulin acts on T4 receptors located on muscle cells, these receptors allow glucose to enter the cell. This is a very good thing, the more glucose you can put into the muscle cell, the less there is too potentially be stored in a fat cell. 

Put simply, a person with good insulin sensitivity is less likely to store fat. Other things that increase insulin sensitivity include walking, sleeping for 8 hours, and fasting. 

Testosterone is an anabolic hormone and its lipolytic. In other words, it helps you build muscle and mobilise and burn fat. You want this right? Ok, do your weight training and do it specifically to build muscle, and ladies please don’t be concerned with ‘getting big’. It takes months of hard work to even build 1-2 lbs of muscle. Keep going, push hard and when you get your body where you want it, just train to maintain. 

GH stands for Growth hormone. This hormone is known as the elixir of youth! This is the hormone that is responsible for the rejuvenation of your body each night during sleep, it signals the body to repair. It’s released during hard physical activity, sleep and periods of fasting. So if you want to stay looking young, these are the things you need to do, lift weights, get your sleep and take 4-5 hour breaks between eating meals.

An argument could be made for weight training raising cortisol, but you’d have to be training at a very high intensity for over an hour. Most people don’t have the capacity to train like that, so no, there are no potentially bad hormonal effects from weight training. 


The insulin effect for walking is as above for weight training, you can improve insulin sensitivity with lots of walking, and it has a lowering effect on cortisol as its very relaxing activity. It’s a low intensity activity and its at low levels of intensity that the body fat pulls more fat to be utilised for energy. A one hour walk would burn approx 400 calories and a large percentage of that could be directly from fat. Plus the more you do something the more efficient your body becomes at doing it, so the more you walk (whilst eating at maintenance or close to it), the better your body will become at mobilising and using fat to fuel it. Walking is absolutely awesome for fat loss, and it should be on your list if being lean is the goal. 

A case could be made that it might raise cortisol if you suddenly went out tomorrow and hiked 10 miles up a mountain, but nobody’s silly enough to do that….. Are they? Build your mileage up gradually and you’ll be fine.  

Kettlebell training 

There are many different ways to train with kettlebells, so it depends on whether you get the positive hormonal effects or not. So let me clarify. 

If you use kettlebells for the purpose of building muscle and/or strength then you will absolutely get the benefits. The more you move from muscle building to endurance, the less of the benefits you will receive. If you do a mix of both, like in my classes for example, you’ll get some of these hormonal benefits, but not as much as you would if you just lifted them to build muscle, however you’ll get additional energy burn which is one of the big advantages of kettlebell training. You can positively influence testosterone, GH, insulin sensitivity, burn a decent amount of energy, and control cortisol.

A case for negative hormonal effects could absolutely be made here, for example if the person in question was doing frequent high volume ballistic work and wasn’t looking after recovery by way of eating well and sleeping well, then you could raise cortisol and suffer the consequences (shuts off fat burning). However this is less likely to happen than compared to running. Its not easy to rack up hours and hours of kettlebell training each week due to the savage effects on your hands. As where it’s easy to rack up hours and hours of running each week, especially when training for a half marathon or some other long distance event.

Again ghrelin release is somewhat an individual thing here, since kettlebell training can be a potent energy burning activity, you could expect some ghrelin release which is the bodies way to say, now you need to replace that energy you burnt by eating. However Grehlin will be switched off within 5 minutes of eating, so if you have practiced slow eating, you can avoid this rebound effect. 


These activities are great for des-stressing so will therefore lower cortisol which in turn could help insulin sensitivity. They do not burn lots of energy and therefore will not raise ghrelin and turn you into a ravenous cookie monster! Since they don’t focus on building the large muscle groups through heavy resistance they won’t have any significant effect on raising testosterone or GH. 

I hope this blog post has given you some insight into how various exercise activities affect your hormones, which in turn drive your behaviours. 

To see this in action, look at the differences between athletes such as body builders or sprinters and long distance runners. 

That gives you all the evidence you need to see how hormones are working for or against you in the effort to have better health and fitness. 

Good luck with your training.