Lost in translation: carbs, fats and our sick nation

2013-12-15 10:00

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One message being lost in the public spat between sports scientist Prof Tim Noakes and his detractors over the validity of the so-called low-carb/high-fat “Noakes diet”: our broken food system is making us fat and sick. Science writer Leonie Joubert wades in as Noakes’ The Real Meal Revolution hits the shelves.

For a long time, we were told that all calories are equal. To keep your weight stable, you just need to balance the calories you graze through the course of a day, with the energy you burn. It doesn’t matter whether those units of energy come from spinach and a mutton chop, or a bowl of pasta alfredo.

Not anymore. If you eat the pasta, we’re now told, you’re not just getting a pile of relatively empty calories (food that has energy, but few nutrients), but when the carbohydrate in the pasta pushes up your blood sugar, triggering a rush of insulin from the pancreas to control that sugar spike, your body switches into fat-hoarding mode.

So your system will bank more of the calories away as fat, relative to what it would have done if you’d had the spinach and chop, which don’t spike your blood sugar as much.

A few hours later, the crash in blood sugar fires up your hunger once more, driving you to eat, pushing up the blood sugar again.

This seesawing locks us into a negative feedback loop of recurring hunger, overeating and overstoring energy.

And this, according to sports scientist Professor Tim Noakes from the University of Cape Town (UCT) Sports Science Institute of SA, is behind today’s soaring obesity rates, along with the conjoined illnesses of heart disease, diabetes and other “lifestyle” illnesses.

According to Noakes, we can reverse this trend by cutting carbs dramatically, and topping up our diet moderately with the one food we’ve been told to avoid for the past three decades – fat, including the big baddy, saturated fats.

Carbs versus fat

A knock-down-drag-out fight took off in the blogosphere after the South African Medical Journal (SAMJ) published a paper by Noakes, summarising the correspondence of 127 people who documented their weight loss, and other positive health spin-offs after switching to a low carb/high fat (LCHF) diet.

The slug-fest was more about scientific method and the “hierarchy of evidence” behind the data for this paper, although it also dipped into the content of the idea Noakes is pushing: that carbohydrates have been given a free dietary pass for decades, and that they’re part of the reason we’re getting fat and sick.

One thing is being lost in the heat of the spat: scientists agree that carbs are a large part of the problem of the “obesogenic” environment, and that fats, including saturated fats, aren’t the dietary demons we’ve been sold all this time.

A whole body of thinking is emerging internationally, calling into question the basis of the “prudent diet” we’ve been encouraged to eat since the 1970s. It goes back to the dietary guidelines issued by the US government in 1977 and is the basis of the food pyramid: the high carb, low fat, “heart-friendly” ensemble of mostly carbohydrates, supporting smaller quantities of more nutritious headline acts of vegetables, fruits, meats, dairy and nuts in decreasing amounts. Easy on the sugar, fats and oils.

Leading the charge in the debunking of the “low fat myth” is a group from Harvard University’s various medical units.

The biology of our blood is complicated, but three things play into our heart’s health, according to the Harvard School of Public Health’s online educational material: bad cholesterol (low-density lipoproteins or LDL) carries cholesterol around the body and can clog our arteries; good cholesterol (high-density lipoproteins or HDL) is the “garbage truck” that mops up excess cholesterol; and triglycerides, fat particles travelling in the bloodstream. You want low LDL, high HDL and not too many triglycerides if you want to keep your ticker in good shape.

Because saturated fat pushes up LDL, we’ve been told for decades to avoid it. But, says the Harvard crew, we replaced these foods with easy-to-digest carbohydrates like bread, white rice, potatoes and sugary drinks, or fat-free or low-fat “health” foods that were high in sugar or refined carbs.

Turns out these are as bad for our LDL/HDL/triglycerides balance as eating lots of saturated fats.

Top notch (meaning, widely published in academic journals) Harvard cardiologist, Professor Dariush Mozaffarian simplified it recently in a Q&A with More magazine: yes, saturated fats push up “bad” cholesterol (LDL), but they also raises “good” cholesterol (HDL). Compared with what carbs do to HDL and triglycerides in the blood, “saturated fats ... are relatively neutral for heart disease risk”.

The Harvard School of Public Health points out that some controversial recent studies haven’t managed to show conclusively that saturated fats cause heart disease. That’s not saying they aren’t linked to heart disease, but a) that the jury is still out until more research is done and b) that previous claims that it was linked to heart disease are up for debate.

The crux of the Noakes vs the critics debate: this question mark hanging over saturated fats and the link to heart health needs to be answered, but that takes time and clinical trials done in an environment free of the lobbying influence of the food and pharmaceutical industries.

Mozaffarian and the Harvard crew caution that we should still keep saturated fats low. But if you replace them with carbs, as the prudent diet has been instructing us, it’s as bad for your heart as eating too much saturated fat. It can even be worse for you, if you’re carbohydrate intolerant, where the body doesn’t process sugars and starches well. They caution to reduce saturated fats (from beef, cheese and coconut oil, for instance) and top up on “good” fats like those from olives, avocados, nuts seeds, fish, and certain seeds.

Carbs are also now linked with heart disease, due to the inflammatory response that happens in the body from sugar/insulin spikes. Meanwhile, the US Brown Medical School is linking high blood sugar and insulin exposure in the brain, with Alzheimer’s – hence a proposal to call this degenerative brain disease Type 3 Diabetes.

Exercise physiologist Dr Ross Tucker, with UCT’s Department of Human Biology, agrees that there is good science to back up this shifting consensus on the fat vs carbohydrate position.

“The value of carbohydrates and the danger of fats have been massively oversold,” he says.

Even one of Noakes’ most vocal critics, Cape Town-based anaesthetist Dr Luc Evenepoel, who has authored a book on weight control, agrees.

“Yes, we were wrong about saturated fats. Refined carbohydrates, rather than complex ones, are probably as bad for your weight and cardiovascular health as too much fat,” says Evenepoel.

So if scientists agree that carbohydrates are making us fat (keeping us in a fat-storing, perpetually hungry feedback loop) and sick (with diabetes and heart disease), why is there resistance to Noakes’ call to revisit the received wisdom of the “prudent diet”?

Mediterranean versus low carb/high fat

If you take the prudent diet – the Mediterranean diet, which was long regarded as the answer to healthy eating, including carbs like unrefined cereals, and other foods like olives, legumes, veggies, fruit – and the low carb/high fat (LCHF) plan, which fares best in terms of weight loss? A New England Journal of Medicine study in 2008 showed they performed equally well (a second study found the Mediterranean was better at weight loss than the prudent diet).

So the prudent diet has been hung out to dry by the arguments presented above. The Mediterranean still holds up as pretty well, according to many.

Although, as health writer Mandi Smallhorne points out, there’s plenty of evidence that restricting carbs improves blood sugar control and other features of insulin resistance – so if you have this diabetes precursor, the Mediterranean diet with its breads and rice and pastas may not be the best option.

Where does this leave the diet which Noakes has finally locked down in The Real Meal Revolution (Quivertree Publications; R298), co-authored with nutritionist Sally-Ann Creed, celebrity chef Jonno Proudfoot and adventurer David Grier?

Firstly, the rather glam science-with-recipes cookbook departs from the low carb/high fat name in order to overcome what Noakes says is a common misconception about LCHF – that it is an eat-as-much-as-you-like binge on fat and protein.

It’s only high fat, relative to the extremely low-fat diet recommended by the food pyramid. Low and high are relative terms, something which is problematic for a generation of dieters who have been told to micro-manage portion size with weighing scales and calorie counts.

Now Noakes calls it the Banting diet, because it was first tried out by William Banting, a “morbidly obese undertaker who (in about 1862) was the first guinea pig of the LCHF diet, reducing his weight so drastically that his approach became known as the Banting diet”.

The book recommends keeping carbs to roughly between 25g to 50g a day.

“This is net carbs (total carbs less fibre), not 50g of potato,” according to the authors, most of which comes from a “green list” of carb-carrying veggies and other whole foods: cauliflower, broccoli, pumpkin, courgettes, aubergines, tomatoes, avocado, leeks, onions, olives and so on.

The no-go “red list”: baked and grain-based foods (bread, pasta, confection), all grains and associated flours, quinoa, bran, breakfast cereals, muesli, granola, mealie products, rice, sorghum and so on.

Now, for the question of fat. Here’s where Noakes and Harvard are out of step. Harvard’s alternative to the food pyramid looks a lot like the Mediterranean diet (plenty of whole grain and whole food carbs; low saturated fats, plenty of unsaturated fats including seed oils).

Banting cuts carbs dramatically, and pushes for saturated fat, not seed oils (these are high in Omega 6 fatty acids, while pasture-raised butter for instance is higher in Omega 3s, which we need more of for optimal heart health).

The froth is about the fact that critics say Noakes is pushing this diet for everyone, not just those who struggle to metabolise carbohydrates. And that he’s making strong claims about the health and efficacy of this diet based on slim scientific evidence.

Noakes is suggesting that the pervasiveness of carb-related illnesses and weight problems, the early success stories of people who have corrected these illnesses by cutting carbs, and the question mark over the link between saturated fats and heart disease, are enough to suggest that we to need to re-think the ratio of carbs to saturated fats to seed oils in our diets. He agrees there is a shortage of evidence – which is why the controversial SAMJ paper calls for clinical trials.

The brouhaha surrounding the SAMJ article, and Noakes’ vociferous public advocacy around the diet, suggests a polarised scientific community that is misleading and confusing the public, notes Tucker.

While these scientists look as though they’re in disparate camps, they’re actually all heading in a similar direction. But the public loses out on critical health-related information in the midst of the firestorm of words, as the true impact of a carbo-loaded diet only now beings to show itself both in terms of our wellbeing and the healthcare system.

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