Dr Caryn Zinn and advocate Dr Ravin 'Rocky' Ramdass

Dr Caryn Zinn and advocate Dr Ravin ‘Rocky’ Ramdass

By Marika Sboros

Three things embarrass New Zealand-based dietitian and academic Dr Caryn Zinn most these days. At university, she never questioned what lecturers said about diet. In her private practice, she prescribed low-fat diets to adults and children for 15 years.  As a university lecturer, she told students low-carb diets were dangerous.

Zinn said this in her evidence led by Advocate Dr Ravin “Rocky” Ramdass, for University of Cape Town emeritus professor Tim Noakes, at the fourth session of Health Professions Council Of SA (HPCSA) hearing against him on October 26.

In Part 1 of a two-part series on her evidence in chief, she explains why she believes that it’s unethical for dieitians who know about  LCHF (low-carb, high-fat) not to offer it as an option to patients.

Zinn was the third of three expert witnesses who flew in to give evidence for Noakes. The HPCSA has charged him with unprofessional conduct for giving “unconventional advice to a breastfeeding mother on a social network (Twitter). That was a single tweet in February 2014 saying good first foods for infant weaning are LCHF.

Tim Noakes

Prof Tim Noakes

She told the hearing that while she has used LCHF in her practice for adults and children for five years, there have been no reported adverse side effects.

Zinn said she prefers to talk of low-carb, “healthy”-fat rather than high- fat because LCHF is really all about “real” food. “When people eat real food, they tend naturally to eat fewer carbohydrates and more fats.”

In her research, she noted “staggering outcomes” from studies on LCHF diets with triple the amount of saturated fat compared to low-fat diets. These were in terms of weight loss and metabolic parameters, such as HDL (high-density lipoprotein) cholesterol, and triglycerides (blood fats).

Especially relevant was data showing that LCHF diets outperformed low-fat in all metabolic parameters.

“Even more staggering” was that LCHF showed a substantial reduction in all inflammatory markers.

“When you are in practice and you read this kind of research, you start thinking about your own ethics and morals,” she said.

Zinn  believes it is unethical and immoral for dietitians to put patients on low-fat diets when they know LCHF is a more effective option.



She said someone should have made all Association for Dietetics in SA (ADSA) dietitians attend the hearing. “It is the best professional development they could ever get – and free.”

ADSA’s former president Claire Julsing Strydom reported Noakes to the HPCSA for the tweet. HPCSA advocate Ajay Bhoopchand told the hearing that he had advised Strydom to stay away after she completed her evidence.

Zinn’s research over the last five years has focused almost exclusively on the LCHF paradigm in public health and sports performance. Projects she has been involved with, which either she or her post-graduate students have led, include:

Public health:

  • Groundbreaking research on hyperinsulinaemia (analysis of a massive dataset). Data showed that a substantial subset of the population with normal glucose curves (supposedly healthy) have elevated insulin levels. This could be the start of chronic disease;
  • Low-carb diets for menopausal women. These women were able to lose weight and maintain it with subtle dietary changes. That was despite many attempts to “diet” using low-fat methods;
  • A12-week randomised controlled trial on members of the New Zealand defence force. Data showed better outcomes for the LCHF group compared with low-fat for weight loss and metabolic parameters.
  • A 12-week feasibility weight-loss trial on “low carb kids”. Aspects included affordability, adherence, acceptability of the food and efficacy (weight loss and metabolic outcomes).

Sports performance:

  • Ketogenic diet for multisport athletes. Data showed a drop in performance short-term but substantial improvements in health outcomes and inflammatory conditions.
  • Low-carb diets for powerlifters gearing up for competition. Zinn’s team found that athletes were able to drop body fat and not lose strength in the lead-up phase.

She will  start research soon into LCHF and the immune system in endurance athletes.

Zinn told the hearing about her nutrition journey and conversion to LCHF. She calls herself a “proudly South African Kiwi”. She was born in Cape Town and has a BSc in physiology and a post-graduate degree in dietetics from the University of Cape Town (UCT).



Ironically, Noakes was one of Zinn’s lecturers at UCT during the heyday of his support for low-fat, high-carb conventional “wisdom”. Zinn said that she “never thought to question” what he taught about  high-carbohydrate diets and “carbo-loading” for runners.

She emigrated to New Zealand in 1995 and did a master’s degree in health science, focusing on nutrition in 2004. In 2012, she did a doctorate at  Auckland University of Technology (AUT). Her  thesis was on weight loss and maintenance of weight loss. She did it very much “through the lens of mainstream thinking about diet and nutrition”, she said.

Zinn is now a senior lecturer at AUT and maintains her private practice.

Prof Grant Schofield

Prof Grant Schofield

Like Noakes, she had her own “Damascene” moment of conversion from the conventional low-fat, high-carb paradigm. The driver was Zinn’s AUT colleague, public health professor Grant Schofield.

Schofield is director of the Human Potential Centre at AUT and does ongoing research into physical activity-based research that includes nutrition. He is also co-author with Zinn and chef Craig Rodger of What the Fat? Fat’s In, Sugar’s Out, and What the Fat? Sports Performance: Leaner, Fitter, Faster on Low-Carb, Healthy Fat

Zinn says she was “ very loyal” to  mainstream low-fat, high-carb dietary  guidelines. However, that changed when Schofield asked her opinion on research low-carb, high-fat related research  five years ago.

Some of it was old research she and Schofield had not come across before. “Or perhaps we came across and never acknowledged it.” As a result, Zinn thought she would “set him straight” by finding all the research that rebutted low-carb, high-fat diets.

She expected to be able to say to Schofield: “Take your low-carb diet and go somewhere else. I am the dietitian and I know because my lecturers taught in my dietetics degree that this (low-fat, high-carb) is how it is.”

Instead, Zinn scrutinised the research. She was soon “flabbergasted” to realise that everything she had learned and thought she knew about diet and nutrition was wrong.

“The evidence that led to mainstream dietary guidelines was largely observational, correlation-based research,” Zinn said. “From a quality viewpoint, it did not compare to the solid, randomised controlled trials (RCTs) that were available to support low-carb, high-fat diets.”

What The Fat

Zinn had helped people to lose weight in her practice but they weren’t able to maintain the weight loss. However, she began to realise that there was good reason:

They were constantly hungry because they were eating too many carbohydrates and too little fat. As a result, she made “a logical leap to LCHF”, Zinn said. It wasn’t just logic, but also because it made sense biologically.

Part of that leap involved understanding why carbohydrate really isn’t an essential nutrient. By that, Zinn means people don’t need to take it exogenously as food (outside the body). Instead, their bodies can produce it endogenously (internally), she said.

Zinn also realised that fears about low-carbohydrate and ketogenic diets were “just scaremongering”. That worried her.

“I went through dietetics school and never questioned anything,” she said.

“Our lecturers gave us these great guidelines but they did not encourage us to ask questions. None of my colleagues questioned anything either.”

As a consequence, Zinn told the hearing: “I’m embarrassed to say that I used to teach my students that low-carbohydrate diets were bad because ketosis was bad.”

Thus, in the end, she simply looked at the biology and the evidence – and changed her mind and her practice.