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How to Lose Weight & Maintain Energy for Ironman Training

Oct 14, 2021

How to Lose Weight & Maintain Energy for Ironman Training

Most athletes are looking to be in peak physical condition for their A race. For endurance events like Ironman where you have to carry your weight across a long distance, performance can be improved with a good power to weight ratio. But it’s a delicate balance between being light, strong and fast and falling into a hole because you’ve under fuelled too aggressively to get there.

Here are my 7 Tips To Drop Body Fat While Still Maintaining Energy Levels And Performance Through An Ironman Build:

1. Eat Strategically

  • Have a periodised approach to your nutrition
  • You shouldn’t eat the same thing every day – your nutrition should match your training load
  • Your nutrition should look completely different on your lighter training days vs a double session hard training day vs a long endurance ride & run off the bike type day
  • Without a specific nutrition plan perfect for you, you run the risk of getting sick or injured
  • Offseason vs training season nutrition should also look different
  • As your training load builds, so should your nutrition throughout the build, rather than eating the same way

2. Get A Dietitian Approved Meal Plan

  • Each training day should look different nutritionally
  • Pre and post-training fuel is important as well as recovery and nutrition across the whole week
  • For an Ironman distance, there are many things that can go wrong with your nutrition, so it is important to work with a dietitian to ensure you have everything under control
  • Your nutrition approach should be individualised, not the same as your training buddy
  • Lots of science, thinking and experience goes into a meal plan to ensure you perform at your best

3. Let Training Drive Body Composition Change

  • If you focus on eating well and fuelling training, you will naturally drop body fat without needing an aggressive calorie deficit
  • Learn how to eat to match training load more closely which will help your body composition shift happen naturally
  • You shouldn’t be eating the same thing each day!

4. Focus on dropping body fat earlier rather than later

  • If you’re doing a 20-week training build for an Ironman – start focusing on shifting body fat earlier, rather than chasing your tail at the back end
  • You can utilise fat-adaptation strategies to teach your body to use fat more effectively so that on race day you're not as reliant on using carbohydrates as a fuel source
  • At the back end of your training build, you want to be fuelling more and practising race nutrition and carb-loading strategies – not starving yourself to lose weight
  • You don’t have to be race weight early but if you’ve got a big chunk of weight to shift, start earlier rather than later

5. You shouldn’t be race weight all year

  • Just like nutrition, you need a periodised weight strategy – you’re not racing all year so you can have some flow to your body composition
  • This does not mean having huge shifts of 10kg+, but an increase of a few kilograms to a comfortable norm is okay
  • Keep your body composition in a closer range to have a better year and perform better without needing to shift huge amounts of weight during your Ironman build
  • Avoid the ‘all or none’ approach
  • Race weight can evolve over time – you don’t need to constantly strive for the same number

6. Slow and steady wins the race

  • Be realistic with your weight loss expectations
  • Slower weight loss helps lose fat rather than muscle
  • 5-1kg/week weight loss is a good target and will help to maintain your energy levels
  • To lose body day, you need to be in a calorie deficit. But to maintain energy levels with heavy training, focus on fuelling training with a little deficit driven by the training volume, rather than entirely food calories

7. Track body composition changes with skin folds, not the scales

  • Track your body composition changes with a measure like skinfolds or a DEXA scan rather than weight on the scales
  • There are many causes of day-to-day weight fluctuations such as hydration status, glycogen fluctuation, bowel movements, hormones etc
  • To get accurate Skin folds – look for an anthropometrist who is ISAK accredited


They are my top tips for trying to lose body fat during an Ironman build, not falling into a hole during it and making sure you maintain your energy levels to smash it come race day!

To go deeper, listen to the Triathlon Nutrition Academy Podcast Episode 12: How to Lose Weight & Maintain Energy for Ironman Training for more!


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