Quick facts on high fat

Low Carb High Fat (LCHF) diets are an exciting new area of research for endurance scientists. Studies show that when subjects adopt a diet high in fat and low in carbohydrates, they flick from using carbohydrates as their predominant form of fuel, to using fat. The benefit to performance is that even the leanest of athletes have fat reserves many times larger than their carbohydrate stores, so they are able to exercise for much longer.

Adopting a diet like this sounds like a no-brainer, but it must be considered carefully.

I will discuss the LCHF diet more, but I first want to state the Trailblazer/Tom Shand view on LCHF:

I believe that everyone is different, and different diets will work for different people. In fact different diets can work for the same person, depending on what is going on in their life at the time. I do not believe the future is Low Carb High Fat, and I do not believe the future is High Carb Low Fat. The future of sports nutrition lies in matching nutrient intake to the individual, their lifestyle, their training programme, and their goals. At some points this may be LCHF, at other points it will be high in carbohydrate. I have learnt a lot from the LCHF movement, and use some of the LCHF principles in my nutrition plans. I like to think of it as a tool that I have up my sleeve to use when the situation is right.

However, in the mean time, there are some important considerations that you must take into account when thinking about this diet.

This is more of a lifestyle than a diet, and the way our food supply works in New Zealand means that many convenience foods are 'off the table', making it challenging to follow properly. The following foods are all drastically reduced with this way of eating, and you have to replace the missing calories (with fat):

  • Bread (and spreads such as jam and honey), wraps, rolls, roti, naan
  • Cereals, oats, and other grains
  • Pasta, noodles
  • Rice, couscous, legumes, lentils
  • Starchy veggies such as potato and kumara
  • Sweet foods such as juice, desserts, muesli bars, puddings

Even if you don’t feel that you will miss these foods, you still need to replace these calories from fat (not protein). Think cream, oils, nuts, seeds, butter, cheese, chicken skin, avocado, and meat fat. If you have weight to lose, you can afford to cut down on the carbs without drastically increasing your fat intake, as long as you are prepared to put up with some hunger as your body adjusts to smaller quantities of foods and your weight loss kicking in. If you are happy with your weight, then you must replace the carbohydrates with calories from fat, otherwise you will either lose weight and/or find it difficult to maintain this diet.

The benefits of using this diet in cycle races is not unanimous. The key issue is that your ability to burn carbs is compromised. You cannot produce energy as fast when using fat as a fuel compared to carbohydrate, so performance is impaired. Fat burning works great when you are chugging away at a constant pace, but if you need to up the intensity, you may not have the grunt and speed of energy supply that you traditionally get from carbs. In an event like the Round Taupo, there will be times when you want energy fast; think hills, catching a bunch, or burning off your mate at the finish line. There is evidence to suggest following a LCHF diet will not work as well in these situations. For recreational cyclists, these situations may be of less importance, and it can be argued that the advantages of being a fat burner outweigh these disadvantages. That is a choice you have to make.

The LCHF diet does encourage an increased consumption of ‘real’ food, which is definitely desirable for optimal health. Likewise, due to the high carbohydrate content in a lot of our processed foods, these unhealthy packaged foods are naturally reduced when following an LCHF diet. This is great for your health, but there is no doubt that it requires greater organisation and planning.

Finally, on the subject of health, the LCHF diet does not discourage saturated (animal) fat consumption, and argues that replacing carbohydrates with saturated fats will not negatively affect your health. Saturated fats have long been associated with heart disease through their affect on cholesterol, so this is a very hotly contested area in the public health community. There is currently little consensus between the scientists on each side of the debate, however most public health organisations such as the Heart Foundation and Diabetes NZ still see saturated fat as something to avoid in your diet. If saturated fat is something which worries you, you can still follow a LCHF diet by using healthy fats such as oils, nuts and seeds, avocado, fish etc.

If it is not done properly, like any diet, LCHF can be detrimental to performance and health. A common mistake is to increase fat consumption without reducing carbs, and the inevitable result is weight gain. There is also little scientific doubt that a high carb high fat diet is bad for your long term health as well!! Talking to a knowledgeable dietitian about all these factors and how they will affect your life is important. Of course I am happy to be that dietitian!

The following are some tips that can help you increase your ability to burn/metabolise fat without compromising your ability to burn carbohydrates and completely changing your lifestyle:

  • Skipping carbs at dinner the night before, and, going without breakfast before your morning training session can encourage fat burning because you have 'low carbohydrate availability'. Consume carbohydrates (and protein) during recovery.
  • Follow a low carb high fat diet on rest days
  • Delay carb consumption during training (i.e take your first gel or food after 60minutes, or even later) during some training sessions (not all)
  • Avoid carbs completely in some slower, less intense sessions. These will need to be over an hour to really challenge and improve your fat burning ability.
  • I try to avoid crossing over into training advice, but the following advice works on two levels. Contrary to the blood, sweat, and tears approach that makes intuitive sense when training, reducing the number of hard 30-90 minute sessions and including more slower, less intense 60+ minute sessions has been shown to produce better results for endurance athletes. This style of training also tends to favour the use of fat as a fuel, and evidence suggests that training like this regularly will enhance your fat burning capacity during exercise.

The important thing is to think about the goal of your training session. If it is high intensity, use carbs to ensure that you are able to push hard (i.e. hill sessions or sprints). If it is lower in intensity, then these are sessions where you can take a lower carb approach. You still want to be able to burn carbs well though, so ensure that on some (I would argue 75%) of your longer training sessions you are fueling optimally using carbohydrates before, during, and after the session.