The fat as fuel debate: Interview with Donal O’Neill

It seems there’s a movement in play. With the low sugar headlines taking storm and the recent research that concluded the low fat recommendations were based on weak evidence, the higher fat, lower carbohydrate way of eating certainly seems to be gaining more mainstream momentum.

What about if you’re exercising though? Things can get mega confusing when you try to fathom sugar in its various forms, carbohydrate intake and a decent amount of physical activity

Trust me, I’ve been pretty confused by it too!

Super fit but with a sweet tooth

Since coaching people to a healthier relationship with sugar, many of those I’ve worked with have been runners or others who are regularly active. They’re healthy and aware of what to eat but just can’t get a handle on the sweet stuff.

It seems it’s not a rare instance for those who exercise intensely to get a bit hooked on sugar (aka fructose). I know I was personally in this place and there’s all sorts of physical and emotional issues that come into play. Read are you a running sugar addict for more information.

It’s not fun…

I used to indulge heavily and then run off the sugar I ate; I used to panic a bit if I didn’t exercise and of course, I used to find myself with very powerful sweet cravings that drove me slightly crazy (well crazy enough to start this website!).

To help with the confusion, recently I started reaching out to interview some of the world’s experts on this topic and today I want to share some very interesting insight from a recent interview with Donal O’Neill – the man behind the Cereal Killers and Run on Fat films.

In the first film, Donal embarks on a high fat diet and shows you what it does to his athletic performance and most importantly his blood work. See the trailer below.

I’d strongly recommend you watch it – it’s only an hour but serves as serious food for thought. You can stream it for $4.99 here.

The second film, Run on Fat is more about athlete level performance but demonstrates some very interesting insight around ‘hitting the wall’. All of this does impact your sugar cravings because it influences the food choices you make when you fuel your physical efforts.

The full interview is here on You Tube, but in case you’re short on time, I’ve picked out some key points and quotes below:

On eating what you want when you’re young…

“It’s one thing for teenagers to eat a bucket load of carbohydrates (or sugar) but the danger is that you establish lifelong habits which over a sustained period of time lead to insulin resistance.”

Do this: Be aware it’s your lifelong habits around sugar (& refined carbohydrates) that can be more dangerous than the actual food in that moment. This is really important point.

On the dangers of being slim…

“40% of people who have develop metabolic disorders are naturally lean and thin so that’s not necessarily any guarantee of your health. It’s a reasonable barometer of health, but it’s certainly not the only one”

Do this: Consider what’s going on inside your body even more carefully if you exercise a lot and are naturally lean or a healthy weight

On not being able to find healthy food…

“People sometimes can have the tendency to reach for the excuse before the better food”

Do this: Take note of excuses. Finding healthier options is often just a habit. Often working around challenges comes down to your creativity and experimentation.

On breakfast…

“There’s a place in Cape Town that serves half an avocado, with cream cheese, pesto and bacon served with tomatoes rocket and olive oil!

Do this: Try it yourself at home one weekend! Donal also takes olive oil out with him to replace sugary dressings – I do this sometimes too!


On using fat as fuel…

“What has been discovered with a higher fat lower carbohydrate diet is that you can reverse ‘hitting the wall’ or ‘bonking’ (as it’s known in America). This happens when the body’s glycogen stores run out – it’s when you see athletes collapsing during a marathon. When you are fat adapted i.e. you use your fat tank of fuel rather than your carbohydrate tank, you essentially eradicate the concept of hitting the wall.”

Do this: Watch the films and then again experiment if you wish. I personally don’t do enough exercise to ‘hit the wall’ but I know I can refuel a 5K run with a high protein, higher fat meal (like scrambled eggs and avocado) and feel great.

On where to start…

“The first thing to do really is just push sugar off the plate. Persevere with this and then make decisions and consider if you want to make other changes”

Do this: Happy Sugar Habits first!! You’re in the right place reading this (make sure you’re signed up to get all the other free help), so just keep going wherever you are until you feel like you’re calling the shots on sugar. Perseverance and commitment it takes but it’s worth it. Focus on this one thing first – I’ve written about this before in what to do when you feel confused by the best diet.


My last words…

Do I eat extreme high fat, low carb? Not completely. Do I eat a lot more fat than I did when I was eating a lot of sugar. Oh yes – it was key in my transition and I definitely feel like I burn fat more effectively as fuel than sugar and carbohydrate now.

So I do embrace LCHF (even if to a less extreme extent) and understand why it all makes sense.

My body has shown me the merits of higher fat, lower (nutritionally weak) carbohydrates, but I also embrace a very non extreme way of eating these days because I believe it was this attitude that caused my sugar issues in the first place.

I still eat rye bread from time to time, enjoy my sweet potatoes and use wholemeal flour to bake with. Currently being in Bali as I write this I can’t really avoid white rice all the time so I do as best as I can.  I just work healthy eating to my own liking and lifestyle free from my former unhealthy habits with sugar and unhealthy attitudes to extreme eating. I think it’s important for me to share honestly where I am because I want you to know that you can find your own blend of things in all this confusion.

I know this has been a mega long post. It’s taken me a near age to craft so I hope it’s helpful!

Have fun watching the films, I’d say watch this space as I expect there’s going to be more on it coming out. At the end of the day listen to your own body and keep working on that healthy relationship with sugar before getting too overwhelmed or caught up in the detail of the rest of it.

What do you think about this topic? Have you any thoughts on experience on using fat as fuel rather than carbohydrates? I’m open to all your opinions and thoughts on this, even if you strongly disagree so please state your stance in a comment below. 

Laura x