Does the timing of exercise matter?

If you’re going to exercise, should you do it first thing in the morning or later in the afternoon?

That’s the topic Diet Doctor Medical Director Dr. Bret Scher, MD, dives into in this week’s DD News video.

In the video, Dr. Scher analyzes and explains research from the Netherlands, which concluded that afternoon exercise has a greater impact on metabolic markers. Earlier this year, The New York Times summarized the Dutch researchers’ 2020 findings in a popular column.

Physiological Reports: Exercise training elicits superior metabolic effects when performed in the afternoon compared to morning in metabolically compromised humans

The New York Times: The best time of day to exercise

The Dutch researchers ostensibly found that exercising in the afternoon, as opposed to first thing in the morning, resulted in better metabolic health improvements in overweight and obese men. The New York Times  called it a “useful study”  and said: “The results add to growing evidence that when we exercise may alter how we benefit from that exercise.”

“These articles really got my attention,” explains Dr. Scher. “Everyone wants to maximize their exercise efficiency.”

But could the study, and the newspaper, come to that definitive conclusion?

Unfortunately, no, says Dr. Scher. “The whole point of my video is to explain why the study was not designed to answer this question.”     

Dr. Scher notes the study had many issues that make it lower quality science, including that the participants were not randomly assigned, but self-selected their exercise times.

Additionally, the researchers did not control for many other variables, such as whether the participants were eating a low- or high-carb diet, how much they ate, or whether they worked out in a fasted or fed state.                                                                                 

However, in the video, Dr. Scher rounds up the other, higher-quality randomized studies that did look at exercise and the time of day, as well as the results of exercising in a fed or fasted state.

Those studies show that working out fasted has more impact, and it is best to fit exercise into the time of day that is right for you and your schedule.

“I’d rather see somebody exercise in a fasted state and eat low carb throughout the day without feeling like you have to fuel up or make up for those calories that they burn. That way, you can burn more fat, you can deplete your glycogen stores more, and that’s going to likely improve insulin sensitivity throughout the day,“ he says. 

“So pick the time that you exercise that’s going to work best for you. If you have flexibility, and you can do it before you eat, that’s great.”

Each week, Dr. Scher takes a scientific study in the fields of nutrition, exercise, or health, or disease and carefully analyses the researchers’ methods and findings. In doing so, he helps you better understand how to judge the quality of various research papers and make informed decisions about your own health and wellness actions. 

You can find more of Dr. Scher’s weekly engaging and informative news videos here, on the DDNews Youtube Channel. Subscribe to the feed so that you don’t miss any of his videos.


2 comments

  1. john
    I'm really interested in this subject and would love to hear more. I'm also trying to establish how to get the best results in my blood sugar levels through diet and exercise.

    I've been keto for nearly 4 years after being diagnosed as type 2 diabetic. After an initial good weight loss and improvement in my blood sugar level resulting in me moving back to pre-diabetic blood sugar levels, my weight started to creep back up. I used all the tips and ideas on Diet Doctor and in other places to overcome a stall, and to maximise results in improved blood sugar level and weight loss. The former was and is most important to me. I have managed to remain in the pre-diabetic range and do not take any medication. In the past 3 or 4 months I have incorporated the advice on Diet Doctor and elsewhere to increase my protein and reduce my fat intake. Before this I was doing the classic LCHF diet - eating lots of extra fat.

    Also, to improve results I have been exercising for the last 18 months or so. In the last few months coinciding with me upping protein and dropping fat I have implemented a HIIT programme consisting of 30 seconds intense work followed by 90 seconds of recovery after a gentle warm up I do 6 sets. I also do weight work too. I changed to this as I found a lower intensity but longer cardio session was causing by blood glucose (pin prick tests) to rise excessively and stay elevated. This was especially true if I exercised in the morning in a fasted state and then remained fasted until an early evening meal. By exercising in the afternoon, especially when I could do this in a fasted state (i.e no breakfast or lunch) and then eating after exercise I found my sugar spike was less and the return to my normal level came about quicker. Of course this could have been caused by a longer fast - or by exercise in the afternoon or maybe a bit of both.

    When I recently had my Ha1bc reading done I was expecting an improvement. To my disappointment I found that my Ha1bc had risen and I was one point off the diabetic range. This was despite me feeling really good and having lost inches around the middle and a small amount of weight. I have gained a noticeable amount of lean tissue (muscle) too.

    After a few days of sulking from my "bad" result I decided to stick with what I was doing as although the Ha1bc was high I felt really good. I spoke with my doctor - who isn't totally supportive of me following the keto / low carb protocol - and I asked if I could have a CGM to see what my diet and exercise would show over say a 2 week period. This was not available on the NHS (UK Health system). So I did a manual testing using pin-prick tests for 2 weeks pricking 20 to 30 times a day, before (immediately) and after (1 hour and 2 hour and sometimes 3 hour) both meals and exercise.

    This confirmed my earlier research that exercise for me was better undertaken in the afternoon - which I tend to do fasted. I often do OMAD on my exercise days (3 times per week); on my rest days I tend to have a breakfast - no lunch and an early evening meal. My eating window on these days is usually 8 or 9 hours. I know it would be better for me to do lunch and evening meal but this doesn't fit so well with my work. The blood results over the 2 weeks appeared to be much lower than the Ha1bc result I had received a few weeks earlier!

    I was interested to read one of Dr Scher's interview blogs with a doctor who had a problem with his Ha1bc reading even though his daily measures were not so bad. ( Sorry can't remember who this was.) I think this was caused in some part by his blood cells living longer than the norm so causing his Ha1bc to be skewed higher - maybe I have this problem too.

    Any way I'm going to continue with my current regimen for a few more months taking some more blocks of 2 week readings all before my next Ha1bc and then take it from there. I'm being patient it took me over 50 years of eating the wrong way to get to T2D so I'm not expecting a magic reversal straight away!

    Thanks Dr Scher and Diet Doctor for your site.

    God bless.

    John

    Reply: #2
  2. William
    Awesome post. Thanks very much. Enlightens my thoughts on my personal habits.

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