Nutrition Strategies to Maximize Fat Adaptation


by Rebecca Dent, Uphill Athlete High Performance Dietitian

It is important to highlight that this article is about the influence of specific dietary strategies on optimizing performance for endurance exercise and is not in relation to health.

Nutrition strategies play an important role in your ability to train and perform well, optimizing training adaptations and aiding recovery, helping you reach your full fitness potential.

In the first article of this series (link) we highlighted that fat adaption training has two purposes:

  1. Enhances physiological adaptations to endurance training (go further, faster, for longer).
  2. Enhances the body’s ability to use fat as a fuel source during endurance exercise (your endurance training) reducing the reliance on carbohydrate during endurance performance (that summit attempt, ultra-race, alpine expedition).

Note that the terminology ‘fat adaptation’ denotes enhancing the body’s ability to burn fat, however the term fat adaptation training is often used to encompass both of the above points (1 and 2).

Nutrition for endurance training is about optimizing fuel efficiency, being able to utilize both carbohydrate and fat as fuel sources. In order for the body to optimise fat as a fuel source there are two main strategies; fasted training sessions at low to moderate intensity and following a carbohydrate restricted diet (low carbohydrate, high fat diet).

Because it takes time for the body to get better at utilizing fat as fuel source anyone who is new to endurance training will need to introduce fasted training slowly whilst at the same time make sure you take on board a source of carbohydrates to fuel higher intensity (zones 3&4), strength training or interval type sessions. There are only a few situations where a high fat diet OR a high carbohydrate diet may be advised. The potential role of a high fat diet for endurance will be discussed in the next article of this series.

Fat Adaptation Dietary Strategies

Fat adaptation specific training sessions, mean carrying out training with low carbohydrate availability in the blood stream, liver and/or muscles and have recently been defined as ‘Train Low’.

To ‘Train Low’ entails dietary strategies that deliberately withhold carbohydrate before, during and after carefully selected training sessions (I.e. low to moderate intensity or zone 1 and zone 2 sessions) (2)

There are several dietary strategies to ‘Train Low’ but we are only going to outline the strategies as advised here at Uphill Athlete, which are perhaps the simplest to apply.

Fasted sessions

  1. Training after an over-night fast:
  • Dietary Strategy: Avoid eating from your last meal in the evening until after your morning training session (water/black tea/coffee/sugar free drinks only are allowed).
  1. OR Training after a minimum of a 4-hour period without eating:
  • Dietary Strategy: If you intend to carry out your fat adaptation session later in the day, you need to allow a minimum of a 4 hours (ideally 6hours) without eating (water/black tea/black coffee/sugar free drinks only are allowed).


In both of the above ‘train low’ sessions, drinking black coffee before training (or 200mg of an alternate sugar free caffeine product e.g. gels, gum, tablet) is often advised. Caffeine ingestion before this type of training has been shown to help reduce the perceived intensity and effort of training (3), quite literally giving you a boost.

Fat Intake During Fasted Sessions

Dietary fat alone is not recommended during fasted training due to the risk of gastro-intestinal upset.

Risk of Illness

Training with low carbohydrate availability places additional stresses on the body and has been shown to reduce immune function and increase risk of illness (2). It is therefore vital that adequate recovery takes place.


What is key to remember is that the above dietary strategies are designed to maximize the adaptive response to endurance training and that if you are new to these fat adaptation strategies then initially training fasted will feel harder to do and performance may likely be reduced during the early stages. It is also important to combine the “fat adaptation’’ sessions with more performance-based ‘‘quality’’ sessions which require an intake of carbohydrate to fuel the session (1).


Coming up next article of this series:

  • High fat diets: is there a role in endurance training and what is the effect of a high fat diet on performance.


References / Links to Further Reading

  1. Louise M. Burke (2015) Re-Examining High-Fat Diets for Sports Performance: Did We Call the ‘Nail in the Coffin’ Too Soon? Sports Med 45 (Suppl 1):S33–S49.
  2. Jonathan D. Bartlett, John A. Hawley & James P. Morton (2015) Carbohydrate availability and exercise training adaptation: Too much of a good thing?, European Journal of Sport Science, 15:1, 3-12