The central idea behind low carb, high fat diets is that by eating lots of fat and protein and virtually no carbs, the body’s metabolism switches from burning glucose (our first source of energy) to burning ketones and eventually goes into a state of ‘ketosis’. Ketones are like a back-up fuel for your body – it’s what we survive off when we burn our own fat in times of starvation. Since fat converts most easily into ketones, low- carb diets recommend lots of high fat meats and dairy products.
This kind of diet has been mutated into various forms from the South Beach Diet to the Dukan Diet in France, the Total Wellbeing Diet in Australia and now the Real Meal Revolution in SA. It is not new, and quite similar to the Paleo or Stone Age diets which shun grains and other carbs in favour of lots of meat, plus vegetables- on the basis that it is what our ancestors ate. But here’s the glitch – this view is actually quite extreme from an evolutionary perspective – since today’s meat is nothing like that which our ancestors ate – and they ate it raw. The body stores toxins in fat and yet the low carb diet advocates eating fatty meat which obviously needs to be cooked. How good is that? And on top of that, we are not talking about organic wild extremely lean antelope with a 5% of its body weight as fat – we are talking about today’s overfed, obese animals which are made up of 40% fat.
The real question, therefore (especially with our increasing desire to steer clear of the endemic of illnesses that are plaguing society today) – is how safe is this diet for us in the long term?
Three main concerns about staying on this diet long-term are kidney function, decreased bone mass and cancer risk, especially of the digestive tract, prostate and breast – apart from the less life-threatening but not insignificant issues of constipation and bad breath. Want some backup to this? A review last year of 32 studies of high protein diets concludes: ‘there is currently no reasonable scientific basis in the literature to recommend protein consumption above the current RDA for healthy adults due to its potential disease risks.’ The risks are listed as (a) disorders of the bone and calcium homeostasis, (b) disorders of renal function, (c) increased cancer risk, (d) disorders of liver function, and a precipitated progression of coronary artery disease.
Let’s have a closer look at one of these risks – the one that would have sparked the most interest; increased cancer risk.
A very recent study from the University of Southern California has found that a high protein diet is associated with 75% increase in overall mortality and a four-fold increase in cancer death risk in people aged 50-65. Isn’t this the very age group who are more likely to diet? The authors propose that the reason for this is to do with meat and milk promoting IGF-1 – an insulin like hormone that makes cancer cells grow faster.
The same cancer concern is also true for a low fibre intake, which is a consequence of eating a low carb, high meat and dairy diet, and is a known and strong risk factor for colorectal cancer. Put these two things together, high meat and low fibre, and you have yourself a recipe for digestive disaster. The emphasis in low carb diets is to eat high fat meat because it is saturated fat that can most easily concert to ketones, and it is these burnt and damaged fats that really crank up the carcinogens.
There is one more potential stick of dynamite – and that’s the high dairy intake, and especially cheese, recommended on the low-carb diets. The trouble is that dairy protein stimulates the body to make IGF-1. This makes cells grow and also helps pre-existing cancer cells to grow, especially of the breast and prostate.
Not convinced? Earlier THIS year a study in the Journal of Nutrition confirmed that the more dairy a man consumes the greater is their risk of prostate cancer. Similarly a study this year in the Journal of National Cancer Institute found that high-fat dairy product intake is associated with higher breast cancer mortality.
To end off- in Patrick’s words exactly ” I remain unconvinced that a high protein, high fat diet, very low in carbs designed to tip you into ketosis, produces any better reversal of diabetes of heart disease, or any greater weight loss or appetite reduction than my kind of low GL diet. However I am convinced that the long-term health risks, especially in relation to cancer, makes this an undesirable ‘maintenance’ approach. “