What is the keto diet?

11 September 2020 Sophie Scott
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“I need to lose weight, so I’m going on a paleo/intermittent fasting/detox/ keto diet, starting Monday. Plus, I’ve signed up to bootcamp 5 x times a week.” Sound familiar?

I often hear this from clients and friends who want to lose weight and are motivated to get cracking. We want to do all the things at the same time!

What we do know about dieting is that it does work… in the short term. The long-term evidence, however, paints quite a different picture. The weight simply just comes back on.  One to two thirds of weight lost is regained within one year and almost comes back within five years. And, at least one in three dieters regain more weight than they lost.

In a recent systematic review, researchers from the University of Minnesota found that the average weight lost on diets was less than one kilogram after two years. What a lot of rules and guilt to go through for such a poor outcome.

People don’t blame the diet for not working; they blame themselves for lack of will power.  There’s lots of shame, body hate and low self-esteem surrounding dieting. Research indicates that dieting is the number one risk factor for developing an eating disorder. In fact, dieters are six times more likely to develop an eating disorder. And, all the restrictions, counting calories and macronutrients can be psychologically damaging, creating a stress response which facilitates weight gain, not weight loss.

So, why don’t diets work? When we reduce energy intake rapidly, the body goes into a famine reaction. This means metabolism slows down, appetite increases and physical activity decreases. These adaptations prevent further weight loss and the weight comes back on.

What is the keto diet?

The keto diet is a low carb, high fat diet and was initially prescribed for epilepsy in the 1920s. Now, it seems everyone is doing keto for weight loss. Why? Because it works. Keto results in rapid weight loss in a short period of time.

Like the Atkin’s diet, popular in the 1970s, keto forces the body to switch to using ketones (a by-product of the breakdown of fat) as the main fuel source instead of glucose. This is termed ketosis and it mimics a fasting state – it is normal reaction when food is temporarily limited and makes the body to rely on its own fat stores.

On keto, carbohydrates are severely restricted to around 5-10% of total energy (equivalent to two bananas a day). This is significantly lower than the Australian Nutrient Reference Values which recommend 45-65% of daily energy comes from carbohydrates to reduce chronic disease risk and obesity.

“A keto diet isn’t recommended for the general population, as the long-term efficacy and safety of the diet are unknown, having only been studied in the short-term.” Dietitian’s Association of Australia

The keto diet is typically low in fibre which in turn affects gut health. Evidence suggests that poor gut health could be linked to obesity. The problem with the keto diet is that it cuts out significant food groups, can cause constipation, dehydration and micronutrient deficiencies. People often report bad breath and keto is classically very difficult to adhere to and lead a normal life. I’ve heard of people using syringes to inject olive oil into their mouths to increase fat intake and saying no to social events because of their dietary restrictions.

New evidence from Yale University indicates that the keto diet in animals may have positive outcomes in the short term, but after a week, can have negative effects. In humans, over one to five years, there is strong evidence that indicates no difference in weight loss doing keto compared with just reducing calories moderately over the week.

In summary, keto seems to work in the short term, but may be a waste of time for those looking for long term weight loss.

So, what does get results in the long term? A slow reduction in energy intake over time, coupled with exercise. Aim for a maximum two to four kilograms of weight loss per month. Having a break from energy restriction is also important to reduce the famine reaction.  This is called interval weight loss. So, you lose a bit, then maintain, lose a bit more, and so on until you reach your goal.


The National Weight Control Registry is a US database of 10 000 people who have lost weight and successfully kept it off for at least one year. It serves as a study to find out why some people are more successful at losing weight than others.

Common characteristics of people who have successfully maintained weight loss:

  1. Eat breakfast every day
  2. Watch fewer than 10 hours of TV/streamed videos per week
  3. Exercise for an hour a day on average.


Dansinger, ML, Gleason, JA, Griffith, JL, Selker, HP & Schaefer, EJ 2005, ‘Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction’, JAMA, vol. 293, American Medical Association, no. 1.
Dulloo, AG & Montani, J-P 2015, ‘Pathways from dieting to weight regain, to obesity and to the metabolic syndrome: an overview’, Obesity Reviews, vol. 16.
IBIS , 2019 . Weight Loss Services – Australia Market Research Report. Weight Loss Services industry trends (2014-2019).
Ketogenic diet, Fad or Future. Professional Development Seminar, Matt O’Neill APD.
Mann, Tracey (2018) ‘Why do dieters regain weight?’ Psychological Science Agenda.
National Eating Disorder Collaboration (2020) Research Portal.
Swinbourne, J 2019, ‘Boden Obesity Management workshop’.
Tomiyama AJ, Ahlstrom B, Mann T.  ‘Long-term effects of dieting: Is weight loss related to health?’ Social and Personality Psychology Compass 2013; 7(12): 861-877.

Sophie Scott

Senior Trainer/Assessor – Nutrition and Dietetics

Sophie is passionate about nutrition, fitness and behaviour change coaching. As a Registered Nutritionist, Sophie takes a wholistic approach to nutrition, focusing on people’s relationship with food, driving a shift to a healthier approach to eating.

Sophie has worked as Personal Trainer and Group Ex Instructor for many years. She has taught a range of group fitness classes from yoga and pilates to Zumba™ and bootcamp. She started teaching at a gym in Vanuatu, then moved to Wellington, New Zealand to launch her own business, fitandfed, focusing on women’s health and fitness, before moving back home to Australia.

Now the Head Trainer - Nutrition at FIAFitnation, Sophie inspires the next wave of fitness professionals and nutrition coaches.

She has extensive experience in the education field, initially working in the area of environmental education, assisting people green up their lives, before moving into the health and fitness industry. Sophie has also presented and written scripts for a number of media outlets including the Eco Reno series on Channel 7’s Sunrise program.

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