When is the Best Time for Ultramarathon Runners to Lose Weight?

By Jason Koop,
Head Coach of CTS Ultrarunning

Let’s face it, there is a good chunk of this readership that would like to lose a few pounds. Whether it’s a byproduct of a few too many adult beverages or a penchant for ice cream (raising my hand), the excess calories that add up to a few pounds around your mid-section can hinder your performance just as much as tying your shoelaces together and carrying around a sack of rocks while running into a headwind at 12,000 feet. Carrying excess weight is particularly problematic going up hills, which can be plentiful depending on your normal training or racing terrain. Realizing this, many athletes have an urge to shed a few pounds right before race day in a last ditch effort to squeak out the last few percent of performance improvement. Unbeknownst to those athletes, there’s a right way and a wrong way to shed those excess pounds (and right before race day is not the best time to do it).

The right way and time to lose weight can leave you leaner and just as fit. However, losing weight the wrong way can be a one-way ticket to underperformance. This was emphasized recently in an article in Applied Physiology penned by a team out of the University of California Davis and led by Dr. Karnie Schall. At its core, weight loss or gain represents the difference between the number of calories you take in and the number of calories you expend. Consume more than you expend and you gain weight. Expend more than you consume and you lose weight. It’s that simple.

The research team looked at the ad libitum energy intake of female athletes undertaking a four-week training overload phase consisting of 130% of their normal volume. You can think of this as training normally at 10 hours per week, then bumping up your training volume to 13 hours per week for a few weeks, which is no trivial increase in in training load. After a subsequent rest phase of two weeks, the research team compared athletes who matched their increase in training load with a requisite amount of energy intake with those who did not. The athletes were then tested for running performance, as well as monitored for ovarian function. Not surprisingly, the runners who kept their energy intake up during the training overload phase showed a positive adaption to the increase in training load, improving performance by ~4%. The runners who failed to match for their energy increase showed a decline in performance by about 9%, as well as suppressed ovarian function.

So, does this mean that you are doomed any time you create an energy deficit in an effort to lose weight? No, but it does mean that you have to be picky about when you choose to do so.

The right times to lose weight

Before we get into the weeds too much on this, it is important to note that weight loss is not universally beneficial for athletes. Even if you feel like you have a lot of weight to lose, in many cases, athletes are better off simply focusing on their training, particularly by making sure they are executing high-quality workouts with enough volume and intensity to improve. In fact, in the history of my coaching career I have never used a specific targeted race weight for any athlete, ever.

Before you undertake any strategy specifically aimed at weight loss, realize that weight loss is relatively low on the performance priority list for most runners. In this sense, nutrition to support your day to day training should be your main focal point and any strategies used to lose weight should only be undertaken if you can continue to support your training despite the energy deficit. In other words, don’t skimp on your training volume, intensity, or volume of intensity just to lose a couple of pounds.

If you are considering losing some weight for your upcoming races, here’s how you can do it right:

1. Be strategic. Pick a time of year where the training load is either moderate and consistent, or being reduced. This can be in between training phases, or even during your offseason.
2. Give yourself time. Target no more than a 1 pound per week reduction in weight for no longer than 3 weeks in a row. In this way, you are essentially cycling your weight loss over long periods of time in 3-week phases. You have to have a long-term lens for this!
3. Avoid compounding stressors. Remember that caloric deficits come at a cost. During times of reduced energy intake, your body has fewer resources to build, repair and regenerate. So, avoid trying to lose weight during periods of intensified training or increased volume (like the research mentioned above).

Using a long range plan, you can strategically incorporate weight loss phases into your training using the three strategies mentioned above.  Note in the example below, I am using the first three weeks of each training phase (denoted by the grey blocks, the dark blue blocks and the light blue blocks) to induce a caloric deficit. The strategy being that the second phase of each type of intensity will be slightly intensified compared to the first. In this example, I would expect this athlete to lose about 10 pounds over a 28-week period, which is completely reasonable and unlikely to result in any negative performance outcomes.

The bottom line

The urge to reduce bodyweight is extremely common among runners, and while losing weight can improve performance for some athletes, but not everyone needs to lose weight, and the effort and training cost of proactive weight loss can do more harm than good. If you choose to pursue weight loss, do it wisely. Give yourself a long runway, induce calorie deficits at strategic times when your training is not at its peak, and overall, don’t compromise your workouts in order to lose weight!