Ketogenic diets or low carbohydrate diets routinely appear in the media with stories ranging from the negative health implications they can have including reduced bone health to the benefits they have on weight loss, diabetes and performance in elite athletes. With such conflicting information out there, let’s turn to the literature to see what the truth is about ketogenic diets and performance.

What Is Keto?

For a diet to be considered ketogenic it needs to contain less than 50g of carbohydrates (CHO) per day, be high in fats 70-80%, with the remaining 15-25% coming from protein. For athletes, especially endurance athletes CHO’s are the preferred fuel source for enhancing performance therefore by restricting CHO intake it forces the body into ketosis. In a ketosis state, ketone bodies (fat molecules) are released from the liver, producing an alternative fuel source to CHO’s.

Why Athletes Choose a Keto Diet

The utlization of fats as fuel becomes one of the primary reasons endurance athletes are attracted to ketogenic diets. This attraction occurs because fats provide a better source of energy than carbohydrates and there is an abundance of fat stores compared to the limited glycogen (CHO) stores in the muscles. Other reasons athletes are attracted to ketogenic diets include, the feeling of enhanced recovery, improvements in body composition and reduced post exercise inflammation.

It is well documented that ketogenic and low CHO diets are beneficial for body composition changes, namely weight reduction through decreases in adipose (fat) tissue. This isn’t surprising considering fat oxidation (fats being burned for fuel) becomes the primary energy source in a ketogenic diet.

Keto Diets and Athletic Performance

In terms of athletic performance the evidence is less clear. Majority of the current studies looking at athletic performance and ketogenic diets routinely involve small sample sizes of elite athletes and over a short time frame (3-10 weeks). As a result, any findings from these studies need to be interpreted and considered with other available literature. With such a specific cohort (study population) transferability of the results to other non-elite athletes becomes difficult.

Exercise Capacity

In terms of endurance performance, there appears to be a reduction in performance during high intensity bouts above 70% of VO2Max when on a short term (3-10 week) ketogenic diet. The postulated causes include; fats require greater oxygen uptake and energy to be broken down compared to CHO, possible impaired glycogen metabolism at higher intensities. However, one study which looked at endurance athletes who were on ketogenic diets for longer than 6 month showed no changes in muscle glycogen stores.

Resistance Training

For resistance training and lean muscle mass it appears that ketogenic diets result in reduced body mass, with conflicting evidence on whether it impacts on lean muscle mass. Regardless, it doesn’t appear to negatively impact strength.

Bone Health

Bone health is an interesting area. An Australian study published early this year revealed that bone resorption (break down of bone) increased and bone formation (new bone formation) decreased in elite athletes (race walkers) while on a short term (3 – 3.5 week) ketogenic diet. This study received a lot of press because the implications are potentially serious; ketogenic diets leading to reduced bone mineral density and bone injuries in elite athletes. However, this study needs to be put into context. It looked at elite race walkers, predominantly males who were on short term ketogenic diets. This is a very specific subgroup of people. As the study rightly points out, further research is needed to understand these findings further before any definitive answer is known about ketogenic diets (short and long term) and bone health in elite athletes and in the general population.

The Wash Up

When it comes to athletic performance ketogenic diets improve fat oxidation and reduce body mass, which is important in endurance sports and weight-class based sports such as boxing, weight lifting, martial arts etc. They don’t negatively affect exercise capacity at submaximal workloads below 70% VO2Max but they do appear to reduce exercise capacity at high intensities. They may also reduce endurance capacity but this appears to be individual, with some athletes being affected and others not. At present, finding the right balance of lower CHO levels which are higher enough not to impact performance at higher intensities is the best approach to maximize athletic performance through a ketogenic diet. One final note, even though CHO intake levels are low, this does not mean an athlete will be running a negative energy balance; energy expenditure should always match energy intake.

[Click Through To Read About Plant-Based Diets]

The Benefits of HIT/HIIT Training

Exercise and physical activity are extremely important for our overall health and wellbeing. With evidence showing physical activity improves; quality of life, sleep, cognition, physical function, insulin sensitivity, while reducing the risks of; clinical depression, dementia, a raft of cancers and chronic preventable diseases, as well as anxiety, blood pressure, weight gain and falls. The current recommendations for physical activity are for 150 minutess per week of moderate to vigorous exercise, this means exercising to an intensity where it is still possible to maintain a conversation but with difficulty. High intensity (with/without intervals) training is a great way of efficiently reaching that 150 minutes per week mark with a host of added benefits.

High Intensity Training (HIT) / High Intensity Interval Training (HIIT)

HIIT refers to exercise that occurs in frequent short burst or “sprints” of high intensity exercise, with recovery periods. The sprints can last from 30 seconds to 4 minutes, with recovery periods lasting anywhere from 1 to 4 minutes and repeated sprints of 2 to 6 cycles per session. For true HIIT to be achieved, heart rate (HR) needs to reach 85-90%+ of max HR during the sprint effort. This is the key difference with moderate continuous training (MCT) where HR will only reach 60-70% of max HR.


In healthy individuals HIT/HIIT programs have been clearly shown enhanced exercise capacity, muscle strength and muscle oxidation compared to MCT. It may also improve cardiovascular fitness and function, as well as anxiety and depression severity. It has been associated with improvements in these same variable in individuals with cardiovascular disease, spinal arthritis and multiple sclerosis, in addition to reducing the disability associated with these diseases. In obese and overweight individuals it is as effective in the short-term as MCT at modest reductions in body fat and waist circumference, which suggests it may be a more time efficient way to exercise. Additionally there is also evidence showing it is well tolerated and has greater improvements in disability and exercise capacity in individuals with nonspecific low back pain when compared to MCT.

What Type of HIT/HIIT Program?

One of the appealing features of HIIT programs are how time efficient they are, especially when compared to MCT. In addition to this, HIIT programs appear to result in similar or greater endurance performances and VO2max (a measure of fitness) when compared to MCT.

Cardiovascular protocols utilizing short intervals (30 seconds or less), for 5 minutes or less, performed 4 or fewer times per week will assist in developing VO2max in the general population. However, the greatest improvements come from longer sprint intervals (2 minutes or longer), higher volume (15 minutes or longer) over a longer duration (4-12 weeks). Resistance training HIT protocols are typically defined as more than 70-80% of a 1 repetition maximum, performed at a maximum of 1 set of 12 repetitions.

Finally, for anyone considering a HIIT program it is important to note that even though HIIT appears to be safe for most individuals, consulting a health/medical practitioner to determine if a HIIT program is safe for you is extremely important before you start any HIIT program.

The Injury Risks From Running

Running season is in full swing at the moment with a plethora of fun runs available, covering 10km, 21 km (half marathon) and 42.2 km (marathon). However, the motivation to run doesn’t necessarily involve competing with others, it could be for stress relief and mental health, general fitness, personal enjoyment or part of a weight loss regime. Regardless of the motivation, injury risks are associated with running where 19% to 79% of runners will experience a running related injury in a given year. Even with improvements in shoe technology helping runners run faster, the injury rates have remained reasonably unchanged since the 1970’s when the modern running shoe was first introduced.

Risk Factors For A Running Injury

Known risk factors related to injury risks in male and female runners include a previous history of an injury, especially in the case of muscle strains and fractures, running with insoles/inserts, and a rapid increase in distance run. There is mixed evidence that absolute high distances (consistently running high distances each week) may or may not be involved with injury risk. Overall, females have a lower injury risk than males however, additional risk factors for women include older age, a longer weekly running distance (48-64km), running on concrete and wearing running shoes for 4-6 months. Whereas males are more at risk if they are restarting running after time away, have been running for less than 2 years and run more than 64km per week. It is also well established that 80% of all running injuries are overuse, this coupled together with the known risk factors for running injuries indicates that training loads play a potential role into why runners experience high injury rates.

Running Load + Injury Risks

What does all of this mean for someone who likes running, it says that although running injuries have multiple causes managing training loads is extremely important to mitigating the risk of injury. With some evidence showing that absolute high training loads can have a protective effect on injury in certain sports, the key is to minimize acute load increases or training spikes. In simple terms this means training loads need to be consistent with small increases in load. A load based model has been put forth called the acute:chronic ratio and it essentially says that the current weeks training load should be between .8-1.3 times the load of the previous 4 weeks of training, if the load is 1.5 times or greater the risk of injury increases.

How To Reduce Your Risk of A Running Related Injury

In lay terms this means if someone is running 5km 2 times per week for 4 weeks and then decides to add a third longer run of 10km a week in the 5th week, they greatly increase their risk of an injury. Does this mean pulling out the calculator to crunch the numbers to get your ratio right, not really. There are plenty of fantastic running training plans available for all levels of runners and all distances, programs that factor in gradual load increases, rest periods and tapering. Running should be enjoyable and injury free regardless of the motivation, so to reduce the risks of sustaining an overuse injury manage the load, gradually increase the kilometres run, avoid training spikes and allow for rest periods. If you do sustain an injury be sure to promptly consult an appropriately trained sports based practitioner/physician.

Supplements Are Big Business!

Sports nutrition supplements, more formally known as nutritional erogogenic aids are part of a supplement industry that is currently booming, with sales in Australia skyrocketing to $1billion dollars per year. It is not hard to miss manufacturers bold advertising campaigns, their lists of powders, pills and liquids for pre workout right through to post workout and recovery, all there to help you “train harder” and achieve “mass gains”. If you do miss the advertising, you cannot miss the plethora of blogs and websites dedicated to sharing what the “best” performance supplements to take are.

Do Supplements Really Work?

But do these advertised supplements actually work? The simple answer is well summed up by Professor Ron Maughan who said “if it works, it is probably banned (by WADA). If it is not banned, it probably doesn’t work.” However, there are some exceptions that we will get to. For elite athletes subjected to drug testing, ergogenic supplements can be a challenging area. Studies show high rates of contamination among supplements with one study ranging from 12-58%, predominantly for prohormones and stimulants. There are also everyday health considerations for non athletes, do you want to be ingesting a supplement containing a banned substances?

How To Protect Yourself From Banned Supplements

Thankfully there are some tools out there to help athletes and individuals to navigate through the challenging world of ergogenic supplements. There are fantastic sites like informed-choice who independently test batches of supplements to determine if they contain banned substances. The Australian Institute of Sport (AIS) also have a sports supplement framework which is based around the best available evidence to determine the safety, efficacy and legality of different supplements.

Which Supplements Work And Which Are Banned?

Using the AIS framework it becomes clear which supplements have strong evidence to support their use and which don’t. Grade A supplements backed by strong evidence which aren’t banned include:

  • Caffeine
  • Beta-alanine
  • Bicarbonate
  • Beetroot juice (nitrates)
  • Creatine
  • Glycerol

Grade B supplements, those containing emerging evidence or deserve further research include:

  • Carnitine
  • Fish oil
  • Curcumin
  • Branched Chain Amino Acids (BCAA)
  • Tyrosine
  • Vitamin C and E

Grade D supplements, those that are on the banned WADA list include:

  • DMAA (stimulant)
  • DMBA (stimulant)
  • DHEA (prohormone/hormone booster)
  • Maca root powder (prohormone/hormone booster)
  • “Peptides”

Don’t be drawn in by the bold advertising nor the websites and forums. Have a thorough understanding of the risks and benefits of any supplements being considered. Consult an appropriately trained health professional to see if you actually need to be taking any supplements at all, it maybe a change in diet and training is all that is required. There are ergogenic supplements out there that have good evidence to support there ability to enhance performance in endurance, sprint and power sports. However, there are also a great deal of supplements out there that have no evidence to support there use and may well even include banned substances, so make sure you know what you are putting into your body.

High intensity interval training (HIIT) is hugely popular in the exercise world at the moment, leading to an explosion of “HIIT” style group classes and work outs. Unfortunately though, many of these classes and work outs are not actually HIIT programs as used in the research literature. Therefore the results individuals achieve won’t be inline with the results HIIT research supports. Is this a bad thing? Probably not, if it means people are exercising this far outweighs the difference in health outcomes comparing HIIT and vigorously intensive classes.

An example of a true HIIT program which was used in a research study using HIIT to treat patients with heart failure involved 4, 30 second sprints at 90% of max HR on an inclined treadmill with 4 minute rest intervals, building up to 6 sprints.