By Stefan Ianev

Does training time really matter?

There is a lot of debate about the optimal time to train both in terms of performance and body composition outcomes. 

Some people swear by training first thing in the morning, particularly in a fasted state. These individuals are either convinced that they will burn more fat training on an empty stomach, or they just feel better and have more energy training first thing in the morning. 

On the other hand, some people prefer to push out their training and sometimes their first meal until lunchtime. And there are others who prefer training in the evening.   

Studies for both aerobic and resistance training have shown that adaptations to training are greater at the time of day at which training is regularly performed than at other times [1,2]. 

This suggests that, at least in terms of performance, the body adapts its circadian rhythm to the time of the day that an individual routinely trains at. 

Therefore, training at a consistent time each day may be more important than the time you train at – especially for resistance training sessions where performance is key. 

If your schedule permits, we recommend doing your resistance training sessions at those times which you normally have the most energy and you are most motivated to train. 

Studies have shown that early bird chorotypes or morning types generally have better performance and a lower rating of perceived exertion in the morning compared to evening chronotypes (night owls) and neither types [3]. Furthermore, evening exercise may exacerbate circadian misalignment in early chronotypes [4]. 

So, if you are a morning person you might be better off scheduling in your workouts in the morning, while if you are an evening person or a neither type you may be better off training anytime from midmorning onwards. 

Now, what about the optimal time for aerobic training if maximum fat loss is the goal?

Many coaches have suggested that performing cardio on an empty stomach may be more effective for burning body fat because if you train after you eat a meal, you will burn off some of the energy from the food that you ate, rather than just burning stored fat.  

While it may be true that you burn more body fat when you exercise in a fasted vs a fed state, that doesn’t necessarily translate to greater fat loss. Studies have shown that body composition changes associated with aerobic exercise in conjunction with a hypocaloric diet are similar, regardless of whether or not an individual is fasted prior to training [5].

The reason is because you will burn less fat for the rest of the day. Think about it for a moment. Suppose you normally consume 2,000 calories per day spread over 4 meals. If you train on an empty stomach, you may burn more body fat, but then you will consume 2,000 calories for the rest of the day. 

If you consumed your first meal, which was 500 calories for example, and then you did your cardio, you might burn less stored fat during the cardio, but that is because you just burned off some of the calories you consumed. However, you will now only consume 1,500 calories for the rest of the day. Therefore, you will burn more fat for the rest of the day and end up at a pretty similar point after 24 hours. 

The take-home point here is that just like with resistance training, you can do your cardio whenever it suits you best.  

References

1. Chtourou H, Souissi N. The effect of training at a specific time of day: a review. J Strength Cond Res. 2012 Jul;26(7):1984-2005. doi: 10.1519/JSC.0b013e31825770a7. PMID: 22531613.
2. Chtourou H, Driss T, Souissi S, Gam A, Chaouachi A, Souissi N. The effect of strength training at the same time of the day on the diurnal fluctuations of muscular anaerobic performances. J Strength Cond Res. 2012 Jan;26(1):217-25. doi: 10.1519/JSC.0b013e31821d5e8d. PMID: 21993020.
3. Vitale JA, Weydahl A. Chronotype, Physical Activity, and Sport Performance: A Systematic Review. Sports Med. 2017 Sep;47(9):1859-1868. doi: 10.1007/s40279-017-0741-z. PMID: 28493061.
4. Thomas JM, Kern PA, Bush HM, McQuerry KJ, Black WS, Clasey JL, Pendergast JS. Circadian rhythm phase shifts caused by timed exercise vary with chronotype. JCI Insight. 2020 Feb 13;5(3):e134270. doi: 10.1172/jci.insight.134270. PMID: 31895695; PMCID: PMC7098792.
5. Schoenfeld BJ, Aragon AA, Wilborn CD, Krieger JW, Sonmez GT. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr. 2014;11(1):54. Published 2014 Nov 18. doi:10.1186/s12970-014-0054-7