Mikki Williden Masterclass: The science of being 'fat adapted' explained

    on December 19, 2023

    This week we share a brilliant expert blog with sports and health nutritionist Mikki Williden, PhD (pictured, right -, who brings her extensive experience as a practitioner and ultra-runner to explain the science behind the benefits of CurraNZ blackcurrants.

    CurraNZ has paid for Mikki's time to review the research, but the copy and opinions here are her own. 

    Mikki writes:

    Our metabolic and physiological health depends on our ability to oxidise fuel for energy, which predominantly refers to the use of carbohydrate or fat.

    Humans are born metabolically flexible and easily able to burn both fat and carbohydrate as fuel. In an ideal situation, people readily burn fat as fuel at low intensities (of which most people have an unlimited supply) and save the limited stores of carbohydrate to be used as exercise intensity ramps up.

    The fuel used when training and competing is influenced both by training status (the fitter the athlete, the easier it is to use fat as a fuel source) and our food environment (i.e., the food eaten).

    'Burning carbohydrate during exercise leads to oxidative stress and inflammation, which isn't ideal'

     In the modern food environment particularly, we can see a preference towards burning carbohydrate over fat even at rest due to the higher carbohydrate load of the diet.

    As carbohydrate is a limited fuel source, and metabolising it creates more oxidative stress, free radical production, and inflammation, this isn’t an ideal scenario for both metabolic health or training and sports performance.

    The enzymes that are required to oxidise fat can be down-regulated over time, reducing the ability to use fat as a fuel source and spare stored carbohydrate.

    As athletes we want to be able to use both fat and carbohydrate, to help fuel over short and long-distance events, and minimise excess free radical production, thus not only improve performance, but reduce inflammation and recovery time.

    Blackcurrant extract has been studied for its potential to enhance fat oxidation in the performance setting in both trained females and males.

    An average improvement in ability to burn fat by over 25% has been found in endurance-trained females (1) in a two hours steady-state cycling test (at 65% VO2 max) when they took the New Zealand blackcurrant supplement over a 7 day period.

    This is notable given that the ceiling at which improvements can be made in a trained individual (with already good fat-oxidation abilities) is generally smaller than that of an untrained individual.

    In another study that trialled various doses (2), researchers found that two capsules (equivalent to 600mg extract) per day provided the best cost-benefit ratio.

    Furthermore, in another study, measuring fat burning during exercise in the heat (3), men and women who took 600mg of the blackcurrant supplement each day for 7 days increased their fat burning capacity by an average of 30%. Researchers tested subjects during 60 minutes of steady state running at temperatures of 34 degrees Celsius compared to a placebo condition.

    This suggests that the supplement may spare glycogen to some extent, which is often burned at a higher rate in more ambient temperatures. While this was not found to be the case in hypoxic conditions (4) as the environment overrode the effect of the supplement, when taken in conjunction with a standard carbohydrate gel over a 120 min treadmill test (5), the supplement was able to increase fat oxidation by close to 25% and spare glycogen use by 11% in a case study analysis.

    While more research is warranted, these are encouraging results for any athlete looking for a competitive edge.



    1. New Zealand blackcurrant extract enhances fat oxidation during prolonged cycling in endurance-trained females, European J Applied Physiology 2018 DOI: 10.1007/s00421-018-3858-3

    2. Dose Effects of New Zealand Blackcurrant on Substrate Oxidation and Physiological Responses During Prolonged Cycling, Eur J Appl Physiol (April 2017) 117:1207–1216DOI 10.1007/s00421-017-3607-z

    3. Dietary supplementation with New Zealand Blackcurrant Extract Enhances Fat Oxidation during Submaximal Exercise in the Heat, Journal of Science and Medicine in Sport March 2020

    4. Effect of New Zealand Blackcurrant Extract on Cycling Performance and Substrate Oxidation in Normobaric Hypoxia in Trained Cyclists. Sports 2019, 7(3), 67;

    5.  Running-induced metabolic and physiological responses by New Zealand blackcurrant extract in a male ultra-endurance runner: A case study J. Funct. Morphol. Kinesiol. 2022, 7, 104.