Top Three Scientific Reasons Why it’s Better to Exercise in the Morning

by Rob Suchet, head coach at RJS Fitness

I am frequently asked when is the best time to train? so I thought I’d write a short blog to help answer the question…

Firstly I should start by saying that for many people the opportunity to pick-and-choose when they train is very limited by their work, family commitments etc. but for those who are able to choose when they train, there are a number of scientific reasons why I advise that it’s always better to train in the morning than later in the day or evening.

The Stress Response to Training

This is the most important reason why I advise people to train in the morning.  Cortisol is an important hormone (similar to adrenaline) which is produced by our adrenal glands in response to environmental stress.  It is an important hormone which helps us get through stressful situations in everyday life and in a healthy individual cortisol is naturally highest in the morning; in fact it rises gradually throughout the night until it wakes us.  During the day cortisol levels should reduce untilwe’re ready to go to sleep again (look at the green zone on the graph below, which represents a normal daily cortisol curve).  Exercise is a stressor on your body: when you exercise your adrenal glands release extra cortisol, increasing your performance in the gym. By training in the morning you will capitalise on the fact that your cortisol levels are elevated already and there’s plenty of time left for them to normalise before you go to bed, but if you train later in the day or evening, your natural cortisol rhythm may be disrupted, making it difficult to reach the deep, restorative level of sleep which is essential for your tissues to re-grow and repair, let-a-lone the other important functions that only occur when the body is in a state of deep rest (liver detoxification, cancer cell destruction).  We use London-based laboratory Genova Diagnostics for our clients’ Comprehensive Adrenal Stress Profile tests which are a very useful tool for analysing your current cortisol patterns, allowing us to tailor lifestyle, nutrition and supplements programmes to their specific needs.

Thermogenic effect of training

Another reason why it’s best to train in the morning is that exercise raises your core body temperature and boosts your metabolism for several hours after you finish training (high intensity training has a much greater effect than steady-state cardio here too).  During this time your body will be using more energy and the body will choose to use fat as the preferred source of fuel, unless you’re eating lots of sugars and starches which will spoil this fat-burning bonus!  Therefore there’s a metabolic advantage to be had from getting your training done before midday.

Increased GLUT4 expression after training

This is where it gets a bit sciency, but this is another important reason why I advise people who want to burn fat to train in the morning.  We have GLUT4 receptors on the outside of all of our muscle cells which helping regulate blood sugar by carrying it across the cell membrane and into our muscle cells rather than allowing it to be converted into triglycerides and stored in adipose (fat) cells.  After high intensity exercise (or weight training) the expression of GLUT4 receptors can be higher than at other times, therefore we can take advantage of this by exercising before a meal or even better in the morning.

What to do if I have no choice but to train in the evening?

If you can only train in the evening here are a few tips to prevent excessive increases in cortisol.  Firstly, keep your training session short and sharp, lasting no longer than 45mins. Next, keep your work intervals intense (heavy) but short (i.e. 10-20secs, avoiding the excess accumulation of lactic acid) and allow sufficient recovery between sets or intervals to feel almost ready to go again (up to 2mins). Long sets and short rest intervals, while very effective for fat burning due to high levels of growth hormone production, cause lactic acid accumulation and become increasingly painful – this level of discomfort places increased stress on the adrenal glands and subsequent increase in circulating cortisol.  Finally, and it probably doesn’t need to be said, but train as early as possible, allowing maximum time between finishing your training and going to bed.

So, train in the mornings to optimise stress hormones, improve insulin sensitivity/blood sugar balance and to burn more fat all day long!


Gregory D. Cartee and Katsuhiko Funai Exercise and Insulin: Convergence or Divergence at AS160 and TBC1D1? Exerc Sport Sci Rev. 2009 October; 37(4): 188–195.

For more information about the issues raised in this blog or our unique approach to personal training, visit or call us at the studio in Bath on 01225 571255.

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