Yeah, yeah. You’ve heard the cliché that breakfast is the most important meal of the day, but that’s a three-balanced, food triangle kind of thing for all those “norms” who never step into a squat rack. For you, meals are for proteining and/or carbing-up, and there may be more or less than three of them, timed to expand muscle and/or shed fat. And you might extend your nightly fast (i.e. sleep) until after your A.M. weight-training. We’ll leave the fat-burning question for another day. But what does fasting do to your strength?
Previous studies demonstrated that skipping breakfast could impair cardio performance. One in 2015, with subjects peddling a one-hour cycling test, showed a 4.5% work reduction even nine hours after skipping breakfast.
A new study addressed lifting weights for moderate reps. Sixteen resistance-trained men who regularly eat breakfasts did two randomized trials after overnight fasts. In one, they ate what the researchers called a “typical breakfast,” but it was high-carb (1.5 g. per kg. of body weight). In the other, they only drank water. Two hours later, they did four sets to failure of squats and bench presses, both at 90% of their 10-rep maxes. When fasted, subjects performed 15% fewer reps overall in the squat and 6% fewer in the bench press, with the greatest drop-offs in the first two sets of squats.
…AND THE FUELED
It shouldn’t be surprising that guys accustomed to exercising when fueled performed poorer without fuel. If you regularly train fasted, you may adapt over time, changing the results of such research. That’s a question for a future study.
Meanwhile, if you prioritize fat-burning over strength gains and benefit from extended fasting, a 6-15% loss of strength (for moderate-rep sets) may be a cost you’re willing to pay. Otherwise, we recommend you eat breakfast, whether or not it’s your most important daily meal. Eat at least one high-protein, complex-carb meal post-sleep and prior to working out to replenish your energy reserves and promote growth.