Training for a marathon is a lot of work, so it can be surprising to some people to find they actually gain weight during the process. While you may find yourself eating more than normal during training, this is not necessarily the reason for your weight gain. There are a number of other factors that can lead to weight gain, some of which are beneficial. Here are some possibilities to consider:
• Increased glycogen storage and blood volume: Novice runners training for their first marathon may experience positive adaptations associated with weight gain, including increased blood volume and increased internal fuel stores (glycogen). This could also apply to endurance athletes who have not exercised in a long time.
• Increase in lean mass: If you have been inactive and started endurance training, that will likely result in an increase of muscle mass in your legs. Add in some strength training and then you’re really increasing muscle mass. Muscle mass takes up less space than fat, so you could become smaller while still staying the same weight.
• Over-fueling: While training requires a lot of fuel, it is still possible to overeat, especially if you’re taking in a lot of caloric food and/or liquid during and after your runs—like gels and sports drinks. Some common instances of over-fueling during training include binge-eating after your long runs when you’re feeling ravenously hungry and eating too much post-run to recover, despite not feeling hungry.
A great way to tell whether your weight gain is beneficial is to check:
• Your body composition: Are you slimmer and do your clothes fit better?
• Your performance: Are you running well and feeling good during runs?
If yes, then don’t worry about the weight change, as it is a normal part of your preparations for the marathon. If no, then you may be over-fueling. However, be aware that actively trying to lose weight before race day can be a slippery slope. Cutting too many calories could lead to reduced energy, impaired recovery, and an increased risk of injury.
Jason Machowsky is a board-certified sports dietitian and certified strength and conditioning specialist at the Tisch Sports Performance Center at Hospital for Special Surgery. He currently serves our nation’s athletes as an active member of the United States Olympic Committee Sports Dietitian Registry. Machowsky received his masters of Science degree in applied physiology and nutrition from Teachers College at Columbia University.