By Jerome Burne
If you know anything about nutrition, and especially if you have friends or people in your family with diabetes, you have probably wondered: Why are diabetics advised to follow a low fat diet?
It means you will eat lots of carbohydrates, which get turned into extra blood glucose. Odd surely when the key aim of diabetes treatment is to keep blood sugar low? Why not begin treatment by cutting your carb intake to a minimum?
It sounds such a no brainer that the next thought is: surely the experts can’t have got it that wrong, there must be a good reason. I don’t know about it. But according to a paper about to be published in the journal Nutrition – there isn’t. An interview with the author, who describes his amazement at The almost totally bogus theory behind the low fat diet is also posted on HealthInsightUK today.
The original paper “Dietary Carbohydrate restriction as the first approach in diabetes management. Critical review and evidence base” has been written by 26 nutrition and metabolism experts and is available here.
Throwing down the gauntlet
The abstract makes the point very clearly: “Dietary carbohydrate restriction reliably reduces high blood glucose, does not require weight loss, leads to the reduction or elimination of medication and has never shown to cause side effects comparable to those seen with many drugs.” What’s not to like?
The paper throws down the gauntlet to the diabetes establishment. “We set out 12 ways in which the low carb diet is the better option,” says lead author Richard Feinman Professor of Biochemistry at State University of New York Downstate Medical Center. “They represent the best documented and least controversial results. They are sufficiently compelling that we feel the burden of proof rests with those who are opposed.” In other words, put up or perform a major U-turn.
The paper is over 20 pages long and fairly dense in places so here is a handy primer that might be a useful starting point for a discussion with your doctor about why you’d be interested in trying a low carb diet.
Why low fat has to be a bad idea
Low carbs used to be the standard diabetes treatment and was demoted, partly as a result of the discovery of insulin – making diabetes a hormone deficiency disorder treatable with a drug. Then when fat became a major cause of heart disease, a low carb high fat diet was clearly a no-no.
We’ll come to the resounding failure of the low fat diet shortly but it is completely accepted that the simple scenario set out at the beginning is correct. High blood sugar is both the main symptom of diabetes and the cause of many of its problems, most likely including the increased susceptibility to heart disease that people with diabetes have. And the most effective way to raise blood sugar it is to eat lots of carbs. A good way to lower it is to eat less carbs..
One of the claims made for the low fat diet was that it was a good way to lose weight because gram for gram fat contained twice as many calories. The rise of both obesity and diabetes while low fat has been the norm has made the claim far less plausible. And the idea wasn’t sensible to begin with. A pound of ping-pong balls weighs as much as a pound of golf-balls. A large American diet survey (NHANES) “indicates that a large increase in carbohydrate as the major contributor to caloric excess in the USA”.
Carbohydrates’ effect on weight comes from the fact that a high level of glucose together with the rise in insulin it stimulates is an efficient fat storing combo. The insulin turns the excess glucose into saturated fat and sweeps it into storage.
And encouraging high carbohydrate consumption is also bad for diabetes because there is a direct link between your blood sugar level – measured by a marker known as HbA1c – your risk of heart attacks and of damage to the tiny blood vessels in the eyes and the feet. This is what leads to the blindness and foot amputations linked with diabetes.
The low fat diet doesn’t now have any legs to stand on
Way back in the 1950 when fat got a bad reputation as the cause of heart disease thanks to the work of Ancel Keys (now shown to be fatally flawed see The Big Fat Surprise – just published) as the cause of heart disease. The case for the low fat diet rested on three legs – it protected the heart, it encouraged weight loss (fat having twice the calories gram for gram as carbs) and it would reduce the amount of dangerous dietary fats in blood stream. But as Professor Feinman’s team shows these claims have now all been effectively cut off at the knees.
For weight loss: “Low carb diets consistently outperform low fat diets for whatever time period they are compared and frequently show dramatically better results,” he writes. This is the sort of result that is regularly reported after three months: 6.9 kg on low carbs vs. 2.1 with low fat. A study of 48,000 post-menopausal women in 2006 could only claim that a low fat diet “did not result in weight gain”.
The results for heart protection have been equally dismal. “More than a dozen studies have failed to show an association between fat in the diet and cardiovascular risk,” Feinman writes. And when different studies are combined in a meta-analysis still no benefit shows up.
One study looking at what happened when saturated fats (most often animal) were replaced with either supposedly health polyunsaturated vegetable oils or carbohydrates, found a “modest direct association between carbohydrates and coronary events”. Carbs were more likely to cause a heart attack.
As we’ve seen the evidence that a diet high in saturated fats raises the risk of heart attacks is thin to non-existent. However there is a link between saturated fats in the blood and heart disease, but unfortunately for low fat supporters, it comes from high amounts of carbohydrates in the diet because of the way insulin is involved in storing glucose as fat.
A study which treated 40 patients with metabolic syndrome (high blood pressure, high blood sugar, unhealthy cholesterol levels and belly fat) with a low fat or very low carbohydrate diet found that low carb was more likely to reduce the amount of saturated fat in the blood even though the low carb diet had three times the amount of saturated fat as the low-fat diets. How is that possible? “That’s what metabolism does, says Feinman, “It’s all about chemical transformation. ‘You are what you eat’ was never a real idea.”
And the woes of the low fat diet don’t end there.
In fact the low carb diet is the best way of reducing all the features of the metabolic syndrome – something that many diabetic patients develop before they a finally diagnosed with diabetes, suggesting it could also be preventative.
A key part of the original case against saturated fat was that it raised the “bad” LDL cholesterol because then as now the common belief is that the higher your cholesterol, the greater your risk of heart disease. After all, that’s the thinking behind doubling the numbers eligible for cholesterol lowering statins drugs.
But recent research suggests several things wrong with this picture. Cholesterol levels are emerging as not very reliable predictors of heart attack risk, so they may not be that important. Several other much less familiar molecules and lipids in the blood – for example, the type of LDL cholesterol described as “small and dense” – are better associated with cardiovascular disease and are more likely to be increased with low-fat diets than low-carb diets.
And there is another reason why a number of experts think saturated fats’ ability to raise cholesterol doesn’t matter so much. This is because it also affects two other players in this complicated dance – pushing up the “good” HDL cholesterol and lowering the number of triglycerides – fat molecules found in the blood. A combination of high HDL and low triglycerides, which a low fat diet doesn’t achieve (in fact it can raise triglycerides) is a sign of cardiovascular health.
The low carb diet comes with a number of clear clinical benefits. Patients are certainly no less likely to stick to them than any other diet, possibly more. The low fat diet is often combined with calorie restriction so you are frequently hungry. The low carbs diet allows you to eat as much as you like because protein and fat make you feel fuller. The result is you aren’t driven to eat more by the swings in blood sugar level that come with low fat.
Because the diet directly lowers blood glucose, what all the drugs are designed to do anyway, many patients find they don’t need so much medication; some are able to stop it altogether. In fact patients on these diets have to be careful they don’t overdose. The authors “caution” that you must reduce your drugs before going low-carb and if you are on drugs, you must work with your physician. “Practicing physicians are not as doctrinaire as the ‘experts’ on health panels,” Feinman says “and will almost always work with you on your diet. If not, get another doctor.”
And finally all these clear clinical benefits come without the side effects sometimes seen with the medication such as a raised risk of heart attack and weight gain.
The challenge to the diabetes charities
So given that the low carb/high fat diet doesn’t come with the heart attack risk that it has been tagged with for fifty years and given that it can do a number of things to cut heart attack risks in diabetes patients that low fat diets can’t, there really doesn’t seem any good reason to keep warning patients away from steak and eggs while being frightfully relaxed about 200 or more grams of blood sugar -raising carbs a day that the official diabetes diet recommends.
Probably the major obstacle to low carb acceptance is a lack of large scale randomised controlled trials (RCTs). You might ask why there haven’t been any, given most of these benefits of low carbs have been known for years. And also why not given the continuing failure of low fat in numerous large trials?
Feinman points out that the central claim of “evidence based medicine” – that all treatments must undergo RCTs if they are to be accepted – is an “absolute” requirement: “unknown in any other scientific discipline.” In law and other disciplines a variety of sources is accepted.
Given the seriousness of the epidemic of diabetes and other metabolic diseases Feinman suggests that: “we have enough evidence of different types to re-evaluate our current recommendations for treatment.”