Breakfast is the most important meal of the day, or is it?

More and more people are starting to skip breakfast. Why though, and what does the science say?

One reason to skip breakfast is to be able to exercise in a fasted state, the main reason for this is to alter macronutrient catabolism during exercise. i.e. the body relies more on fat as a fuel when exercising fasted. As well as burning fat during the exercise you adapt to become a better fat burner. This is the ‘train low’ paradigm popular among athletes.

The other reason often mentioned is to lower your total energy intake during the 24 hour day, the most critical measure of energy intake. One study has found skipping breakfast prior to exercise may reduce overall energy intake¹ however this was very limited in design to only one meal after the fast period.

Another more recent crossover study looked at this in more detail². Groups did a week of no breakfast, exercise, then ad libitum eating (fancy word for eat as much as you want) then a week of breakfast, exercise and ad libitum eating.

What happened? There was no big difference in energy intake at lunch, but dinner was significantly bigger when breakfast was eaten. So much bigger that in terms of total energy intake during the day, when breakfast was skipped total calories were 25% lower.

This is the first time I’ve seen a study that’s shown reduced total energy intake on fasting days was due not just to the fact that breakfast was skipped but also a decreased energy intake later in the day and thus that fasting before exercise may suppress energy intake throughout the remainder of the day.

This, if reducing your total energy intake is your goal, i.e. you want to lose weight, would be a great reason to skip breakfast.

As a final point though remember, as with most things diet and nutrition, what’s most important is compliance and how things work with your lifestyle. Feel rubbish if you skip breakfast? Simple, don’t. If on the other hand like me you feel great running or exercising fasted first thing in the morning, or when commuting skipping breakfast is convenient, go for it! Just remember the only breakfast rule, if it can be delivered to you in bed you have to eat it.

¹ J. T. Gonzalez, R. C. Veasey, P. L. S. Rumbold, and E. J. Stevenson, “Breakfast and exercise contingently affect postprandial metabolism and energy balance in physically active males,” British Journal of Nutrition, vol. 110, no. 4, pp. 721–732, 2013

² Jessica L. Bachman, Ronald W. Deitrick, and Angela R. Hillman, “Exercising in the Fasted State Reduced 24-Hour Energy Intake in Active Male Adults” Journal of Nutrition and Metabolism, Volume 2016 (2016)