Are high-carb diets a big fat mistake?
After years of advocating a high carbohydrate/low fat diet for athletes, Professor Tim Noakes has done a nutritional U-turn.
Turning the teaching of the past few decades on its head, Noakes, 61, professor of sports science and exercise at the University of Cape Town, now says it’s not carbohydrates we should be loading, but protein and fat.
So convinced is he of the accuracy of his new-found theories, he has even gone so far as to say that anyone who has his book, Lore of Running, should “tear out the section on nutrition” because he no longer believes the high-carb advice is best for all athletes.
His low-carb teaching is not exclusively for athletes either.
Noakes believes a large part of the population could benefit too.
The high-carb/low-fat mantras of the past years have not worked, he says, because obesity levels and chronic diseases of lifestyle (CDL) have soared. The very diet that was supposed to prevent CDLs appears to have been fuelling them.
“Since adoption of the ‘prudent diet’ which restricts fat intake with an increased intake of carbohydrates, the prevalence of adult-onset diabetes and obesity has increased explosively,” he says.
“It is the ‘elephant in the room’ with which advocates of the prudent diet are completely unwilling to engage. Until they do, their advice is open to question.”
So, how did the change of heart come about?
Noakes’s interest was piqued by the publication of the 2010 US Dietary Guidelines which promoted the concept of the food pyramid built on six to 11 daily servings of bread cereals, rice and pasta.
It started him on a path of investigation into the role of carbohydrates in the body.
He delved into the low-carb theories of science writer Gary Taubes in Good Calories, Bad Calories and Why We Get Fat and What to Do About It.
He also discovered that his low-carb eating plan was first prescribed in 1861 by Harley Street surgeon, William Harvey, to London undertaker, William Banting, earning it the name the Harvey/Banting diet. Banting became the standard treatment for weight loss until it went out of fashion in 1959, replaced by the current “heart healthy” high-carb/low-fat diet.
Dr Robert Atkins rediscovered banting in 1974.
The more Noakes read about low-carbohydrate diets, the more convinced he became that not everyone was designed to metabolise refined carbohydrates, including cereals and grains, efficiently.
“Cereals and grains have been a staple of the human diet for only the past 20 000 years, whereas we began to eat meat perhaps 2.5 million years ago,” he explains.
Noakes says he has a personal interest in this theory too, because he has a biological predisposition to develop adult-onset diabetes because he is “carbohydrate resistant” and therefore pre-diabetic.
“My biology is such that I am unable effectively to clear glucose, the breakdown product of ingested carbohydrate, from my bloodstream. As a result, my pancreas must over-secrete the hormone insulin, which normally directs the glucose from the bloodstream to the liver and muscles.
“In my case, most of the carbohydrate that I ingest is directed into my fat cells by the action of insulin each time I eat carbohydrate. Then the insulin locks the fat in my fat cells and prevents its release as energy for as long as I continue to eat a high-carbohydrate diet. This leads to progressive weight gain, continual hunger, lethargy, and in time, pancreatic failure and the onset of an irreversible and universally fatal condition, adult-onset diabetes. But the solution is simple – cut down the secretion of insulin by eating a minimum of carbohydrate.”
He decided to experiment on himself, avoiding all bread, cereals, rice, pasta and refined carbohydrates and stocking up on healthy meats, fish, vegetables and fats, including nuts.
Results were spectacular. After five months, he lost 15kg, was at his lowest weight in 30 years and running faster than he had in 20 years.
He says: “It has taken me 61 years to suspect that bread and cereals – the biblical staff of life – as well as rice, pasta and refined carbohydrates may not be as healthy for me personally as I had always believed.”
He also found that he could maintain his ideal body weight without any sense of deprivation.
“Protein is a potent appetite suppressant perhaps because a too-high protein diet is toxic to humans. As a result, low-carbohydrate diets with increased protein do not cause the frequent sensations of hunger and privation that accompany calorie-restricted, high-carbohydrate diets.
“The absence of hunger is more likely to encourage compliance and sustained weight loss. In contrast, there is an addiction, especially to rapidly assimilated carbohydrates like sugar and refined carbohydrates, that drives the over-consumption of all foodstuffs, carbohydrates especially, and hence leads to weight gain.
“Thus my untested theory is that it is the unrestricted intake of especially unrefined and hence addictive carbohydrates that fuel an over consumption of carbohydrate calories. In contrast, a high-fat intake does the opposite – it breaks the carbohydrate addiction and reduces hunger because the stored fat suddenly becomes available to the body once more.”
Noakes stresses that this is not blanket advice for everyone. It is not a quick fix for weight loss and if you go back to your old eating habits, you will regain your weight.
“The metabolic abnormality (CR) is never going to normalise regardless of how much weight is lost or how much exercise is performed. For those with CR, our metabolism is the problem and we have to change the nature of the foods we eat, for ever. It is easier than most would believe.
“However those who can metabolise carbohydrates efficiently and who have always been lean despite eating a high-carbohydrate diet may not benefit in any way from this eating plan. I would not advise any athlete who is lean and quite happy with his or her weight and performances to change to this eating plan since it might not make a difference and might even be detrimental.
“I do not believe that I have the final answers and am continually reading the scientific literature and the internet and tweaking my diet. I will continue to modify my eating by studying the literature, eating differently for periods and seeing if I notice any differences in how I feel, in my blood markers and in my running performances. But the basic pattern of severely restricting my carbohydrate intake remains completely non-negotiable.”
Noakes advises people to consult a registered dietician before changing their diets – but finding one that supports his theories could be a challenge.
* Excerpts in this article were taken from Noakes’s articles in Discovery Health magazine and on Health24, and used with Noakes’s permission.
There’s no guarantee yet Noakes’ theories will work
Dr Harris Steinman, of the Food and Allergy Consulting Testing Services, says:
“You cannot extrapolate that the diet effective for Noakes will work for you. There is a growing realisation that one’s phenotype (the interaction of your genes with other factors like the environment) plays a role. In essence, the dietician or health professional’s responsibility is to evaluate the particular parameters of a specific individual and to construct a specific diet which will be more likely effective (and safe) for that individual.”
Berna Harmse, president of the Association for Dietetics in South Africa (Adsa), says obesity is multifactorial in nature and it is difficult to give one food group the blame.
“It is true that a low carbohydrate diet is prescribed for patients with insulin resistance, but one must be careful not to extrapolate to the whole population and definitely not before more clinical research is done.
“As registered dieticians, our function is to firstly evaluate a person’s habitual diet, and according to the recent findings in the scientific literature, make appropriate changes to facilitate a lifestyle change.
“There is an abundance of literature to say that it is not the carbohydrate per se, but the amount and quality of carbohydrate that is the problem. Refined carbohydrates are not meant to be the staple of our diet, but rather high fibre options. It is about balance and moderation. Healthy people should try to include all food groups.”
Dr Luc Evenepoel, a specialist in anaesthesia and intensive care and author of a book on long-term weight control, says:
“To assume that carbs are the only causes of obesity and lifestyle diseases is presumptuous. They might be, but it is far more likely that the causes are multifactorial. In rural Asia, everyone is slim, yet they eat almost purely carbohydrates (rice, noodles, vegetables). There must be people among them who have some carbohydrate resistance, as Noakes calls it, yet they’re all slim.
“Being so vocal about his new way of eating is maybe not such a good idea. Noakes knows he is famous, and should realise that people – most of them desperate and poorly informed – are going to imitate him. For the majority, this is going to backfire badly. They look at low carb-high fat as the salvation they have been waiting for all those years.
“If they are not going to introduce other, equally important changes to their eating habits as well, I can guarantee them they are not going to keep the weight off.
“Weight loss is irrelevant if the weight is not kept off (losing and then regaining is worse for your health than not losing at all). His diet has been found over and over again to be unsustainable.
“Let’s talk again in four years’ time. If Noakes has managed to keep his weight off, we can start spreading the message.
“If he hasn’t – the most likely scenario – his new eating plan would have been something he, like the countless weight messiahs before him, should rather have kept quiet about.”
Noakes’s food choices
“I don’t count calories or worry about portion sizes because I don’t need to.
“My body weight is now regulated effortlessly whether or not I exercise vigorously each day. Once you find the amount of carbohydrates that is ideal for your body, your hunger disappears and you exist in a state of perpetual satiety. Under these circumstances, your brain will direct you to eat only the exact amount of energy that the body requires each day.
“Your subconscious brain is a much better regulator of your required energy intake that your conscious mind can ever be.
“I eat organically and supplement with omega-3 fatty acid capsules. I am also experimenting with a range of vitamins.”
OUT: Sugar, bread, rice, potatoes, breakfast cereals, pasta, porridge, high-kilojoule fruits, cakes, sweets, artificial sweeteners
IN: Eggs, fish, meat (unprocessed); milk, cheese, yoghurt (all full cream); vegetables like broccoli, tomatoes, mushrooms, onions, avocado (low carbohydrate); nuts (macadamias, walnuts, almonds), not peanuts or cashews; fruits (lower carbohydrate fruits, like berries and apples) and water, tea and coffee (all unsweetened).
How do you know if you are carbohydrate resistant?
* Family history – is there a close relative with adult-onset diabetes?
* Were you obese as a child or has there been progressive weight gain throughout your life?
* Have you gained weight or been unable to keep weight off for any length of time despite eating a calorie-restrictive high carbohydrate diet?
* Advanced carbohydrate resistance can be diagnosed with a fasting blood sample.