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Best Time to Exercise to Burn Fat

Updated: Feb 22

In this video I read an excerpt from Dr Greger's book titled 'How Not to Diet' (page 376-77) about exercising before or after consuming calories to lose the most weight. Below is a transcription.

Main Points:

  • Studies have shown that exercising before consuming any calories (drinking coffee is okay) results in burning at least 50% more calories compared to exercising after eating breakfast and/or lunch.

  • In one research, male study subjects burned 1,142 calories after running for 100 minutes before breakfast, compared to burning 608 calories burned when running 100 minutes after eating lunch.

  • Another study was done with female study subjects walking instead of running, and the results on average was an increase of 60% more calories burned when exercising before consuming calories compared to after.

Excerpt (as read in video above):

Simply because you burn more fat while exercising doesn't necessarily mean you end up with less fat at the end of the day. Maybe our bodies offset the extra fat loss that occurs during exercise with a little extra fat storage when you finally do eat, balancing out the equation. Researchers in Japan set out to investigate this possibility by measuring 24-hour fat balance after 100 minutes of running either before breakfast or after lunch. On the exercise-after-lunch day, subjects burned a total of 608 calories of fat over the course of that day. In contrast, on the exercise-before-breakfast day in the same 24 hour period, they burned through nearly 90% more -- 1,142 calories of straight fat. So the next day before breakfast exercises woke up with about a quarter cup less fat after the same amount of exercise. Remarkable!

Running for 100 minutes is pretty hardcore, no matter whether you do it before or after breakfast. What about something less intense, like walking? Study subjects walk for 60 minutes at different times of the day -- before breakfast, after lunch, or after dinner -- and also had a control day where they didn't exercise at all. Over 24 hours, they burned off 432 fat calories after exercising in the evening, and 446 calories after walking in the afternoon. On the exercise-free control day, however, they burned through 456 calories. It's almost as if the post lunch and post dinner walkers hadn't walked at all. What about a pre-breakfast walk? The same amount of exercise before breakfast resulted in 717 calories of fat loss. Over the course of a day, timing truly does matter.

End of Excerpt

(I have to include a picture somewhere on this page otherwise a thumbnail image won't appear)

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