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Timing Breakfast to Optimize Performance

What’s more important—fitness gains or weight losses? Breakfast may be the link between both.

ZonePerfect Breakfast

Tell someone you’re a health, nutrition or fitness professional and the questions begin. As a RD I’ve been asked to calculate nutrient needs by complete strangers, am constantly peppered with diet du jour questions, and cannot get through the week without being asked about breakfast. Is it necessary? What should it include? or not? And, my favorite, “would it be better to skip breakfast or eat a donut if that’s the only option?” I’m all for everything in moderation but seriously?!? I’m not even going to answer that one.

Why does this sunrise meal continue to confuse us? Is it really the most important meal of the day or was that slogan just clever marketing? In truth, it’s complicated. As a registered dietitian, I find a lot of benefit to a well-designed breakfast. This meal is beyond crucial for growth and cognition in the young.  And for all of us, purposeful intake of fiber and high quality protein sources- think Greek yogurt, ready to drink shakes like Carb Wise, or an egg and spinach omelet) can improve nutrient density across the day, supplying micronutrients and fiber, and energizing an individual to tackle the day ahead. Research also finds that non-active individuals who skip breakfast are more likely to reduce activities of daily living and therefore overall energy expenditure throughout the day. In other words, omitting this meal won’t help every single person move towards an overall goal of better health and wellness.

But what about motivated clients willing to move more, and pursuing significant changes in weight but getting frustrated by stagnant numbers? Exercise training interventions often report these smaller than expected fat and body mass losses and it’s probably no surprise that this response can be explained by many factors. Over-compensation of energy balance behaviors, increased hunger following exercise, or a reduction in activities of daily living following exercise sessions are common culprits. These reasons alone and in combination can effectively undo the energy deficit created by the energy expended through exercise.

So what to do about breakfast? Dive in or skip entirely? For those clients seeking health gains over performance gains, skipping breakfast before a morning workout may be a great ally in the quest for weight loss. A study by Edinburgh and colleagues examined the total daily energy deficit created by exercising in a fasted state (sometimes referred to as “training low”) and found that the caloric deficit created by skipping this meal as well as the energy expended during exercise amounted to 400 fewer calories across the day. Study participants who consumed breakfast (431 calories of oats and milk) and cycled for 60mins didn’t create a significant caloric deficit across 24 hours and one could argue their weight would remain steady.  Individuals who consumed the same breakfast but rested afterwards ended up in 24-hour positive energy balance with +492calories. In other words, skipping breakfast and then cranking it at the gym could be a useful strategy to induce a short-term energy deficit.

Additional research has found support for the practice of training low but experts caution implementation on a case by case basis.  Many athletes and fitness enthusiasts with weight loss and fat adaptation as a primary goal are already implementing fasted training into their day to day routine.  The theory is this; by training in a fasted state, perhaps as a result of a “sleep low, train low” habit, an intermittent fasting plan excluding fueling before or during a workout, or as a result of a hurried morning with no time to grab breakfast before practice, individuals who show up on E must get through the workout fueled by endogenous stores rather than exogenous sources. This reliance on endogenous fuel, primarily fat stores given that glycogen is limited, might promote fat adaptation and potential shedding of the padding that we are all so desperate to burn off.  However, we should all realize that to stimulate select endurance-related adaptations (i.e central changes such as cardiac hypertrophy), high glycogen conditions or training in a fully fueled state is superior, given that having fuel on board allows for the completion of more work performed and, of course, an elevated heart rate for a much longer training duration.

To simplify and determine if breakfast is best for you and your client, follow the mantra I suggest in my recent book, Sweat. Eat. Repeat.:

Light workout &/or primary goal of weight loss? Deplete before you eat.

Intense workout or looking to PR?  Eat before you compete.


Edinburgh RM, Hengist A, et al. 2019. Skipping Breakfast Before Exercise Creates a More Negative 24-hour Energy Balance: A Randomized Controlled Trial in Healthy Physically Active Young Men. Journal of Nutrition Aug2019, Vol. 149, Issue 8.

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