Many official sources for years have been talking about low fat diets (meaning high carb, low fat) and promoting this as an ideal eating pattern. The UK government for years has been promoting its Eatwell Plate, now called Eatwell Guide as an example of a “balanced diet”.
The question I have to ask is, does this apply equally to all people? You wouldn’t tell someone who is lactose intolerant to have more dairy products, but oddly it is common to think that diabetics (which at its core is effectively a carb intolerance) should eat more carbs.
Today I am looking at one report entitled: Overweight and diabetes prevention: is a low-carbohydrate–high-fat diet recommendable? published online March 14th, 2018 from the European Journal of Nutrition.
I started looking through this and found that while there was much sense in the article, I was frustrated by the inferences made from poorly argued viewpoints. The most common problem was making a claim that one diet was bad simply because another diet was better than “doing nothing”. That’s like saying that “This soap is so good it shows a 80% improvement over not using soap at all”.
One quote said:
Sardinia, Okinawa (Japan), Loma-Linda (California), are intriguing, given their commonality is their relatively high-carbohydrate and low-saturated fat content of their daily diet, which allow them to stay healthy until very high age. The Okinawa inhabitants, for example, originally ate a daily diet that contained an amount of carbohydrates that exceeded daily energy intake by 60%, consisting primarily of sweet potatoes and the foliage, supplemented with seaweed and fruit. The recent introduction of a more Western lifestyle, containing more saturated fats, added sugars and alcohol, has gone to the significant detriment of the longevity prospects of the youngest generation [22], which indicates that diet (carbohydrate and fat quality), in combination with other lifestyle factors is crucial for health.
All this shows is that eating high carb AND high fat is detrimental. I don’t recall anyone ever debating that. The high carb diet worked for them – because of their activity (and the fact that their bodies were acclimatised to it). Adding fat AND sugar to their diet caused problems. That doesn’t mean that adding fat to their diet was the problem – just that adding BOTH was. This is generally accepted by everyone so why is this being brought out? It stands to reason that if you add fat you need to reduce carbs.
The paper then goes on to ask why a Low Carb High Fat (LCHF) diet should be even considered given that it apparently has a poor adherence. I do think that as it is considered to be challenging should prompt people considering it as there are few things less motivating than falling off your diet. However I do not think it should be discounted simply because it may be too hard. It may be too hard for some – but for others they may manage fine.
Next is a discussion on high carb and if it is unhealthy. Oddly this paragraph never attempts to answer this question, preferring instead to talk about the so called Paleo diet and point out that people at that time did not eat the way proponents of the Paleo diet claim. This may or may not be true, but doesn’t really answer the question on the health questions over high carbs. One thing it does say is that the quality of the carbs – not quantity is most important. I personally have to agree with this in that quality is important.
I would also add that there is often disagreement as to what carbs actually are. Fibre is technically a carb but doesn’t behave in the same way. Insoluble fibre for example does not turn to glucose in the body, it adds bulk and helps food “pass” more easily. Soluble fibre on the other hand is converted to glucose like other carbs, but it turns to gel and slows digestion. It therefore provides a more slow release energy (thus reduces the sugar spike and drop). Fibre is generally (by both sides of the argument) considered important. Adherents to a carb rich diet often point at fibre as a problem for low carb diets. However it is still possible to have enough fibre with a low carb diet. Low carb in these diets more correctly are low carb (that is not fibre). For example if 10g of a carb contains 8g of insoluble fibre it would be incorrect to count its carb content as 10g, as the insoluble fibre should not be counted. It would be more correct to label this as 2g of carbs.
There is later a section called “What do meta-analyses of LCHF diets tell us?”. This was a confusing read as it then went on to talk about high carb, low fat diets which is the opposite of the title. It made a large deal out of the fact that starting with a diet of 35% carb, 35% fat, and 30% protein, half stayed as a control group and half changed to 10% fat (while presumably increasing carbs). It then says that the people who changed to 10% fat did better than those that had high fat and high carb. This is news? Of course having high fat AND high carbs will be worse.
Another statement says that many food authorities recommend relatively high-carb and high-fibre. This may be true – but these should not be treated as one item. One of the biggest flaws in the high carb camp is that they assume you have to eat high carb to get enough fibre. It may be easier to do this on a high carb diet – but it isn’t essential. You can get enough fibre on a low carb diet too.
It is true, as stated in some of this research that an increased level of fat in low carb high fat diets have been shown to (sometimes) increase LDL cholesterol. This may be dependant on the person’s genetic makeup but one difference between fats eaten many years ago and those eaten today is the prevalence of highly processed fats. It is believed by some that natural saturated fat (and an absence of highly processed fats in the diet) do not increase LDL and that the real culprit is the increase in highly processed foods.
Much is said in this article about adherence to low carb high fat diets and the fact that people often do not follow them correctly. For a true LCHF diet, it is usually stated that the carbs should be less than 20g a day. With this carb intake, it is important to add extra fat – as your body does need something to burn – and adding fat will enable ketogenisis to work. However one of the key arguments against LCHF diets is that when people do not stick to them, but still add the fat while eating 150g+ of carbs a day, the diet fails. However I do not think it is fair to say the diet doesn’t work itself if people simply do not follow it. The most that can be said here is that it seems hard to stick to – so one of the biggest questions people should ask is if they realistically will be able to stick to the diet. Remember that this isn’t a “diet” in the sense of a short term thing – this has to be a total lifestyle change.
The second key argument against LCHF is the claim that there is not enough long term data to show its long term (20-30 years) effects. However It does seem a little strange to dismiss an option simply because it does not yet have long term data.
Additionally negative effects on LCHF diets often rely on data that high fat diets may be detrimental but these diets are not specifically low carb – but high fat. They could be high carb, high fat, low protein just as easily. It is probably very true to say that you can make either a LCHF or HCLF diet – more or less healthy depending on the quality of food eaten. Highly processed foods again are a prime culprit.
At the end of the day – it is clear that the difficulty in obtaining clear guidance is a problem. It is also apparent to me that LCHF diets are challenging to keep adherence to so probably are not ideal for those what do not believe they can keep to them.
It is also apparent that quality is important: quality of the carbs eaten, quality of the fat eaten. Two areas that are agreed upon by both camps are the reduction of highly processed foods, and the importance of activity (exercise). Fresh food such as above ground vegetables, healthy oils such as extra virgin olive oil are mostly recommended for both high and low carb diets.
