I’ve spent my last few posts focusing on some very bad studies that have been prominently featured in the media lately. Now I’d like to discuss a recent study that has gotten less attention, but that I think is far more interesting and useful. However, before I get to the study itself (in the next post), I need to go into some background.
From the 1940s onward, a large body of evidence across many different studies started to emerge suggesting that – on average – higher cholesterol levels were a risk factor for cardiovascular diseases such as heart attack. The history of this research is too long, too complex, and too controversial to go over in depth here, but what’s not in dispute is that by the 1980s, most doctors had coalesced around the idea that high cholesterol is a risk factor for heart disease, and that lowering cholesterol could cut this risk. And to be clear, nothing that I’m about to state in the rest of this post should be taken as disproving this belief. It is still the case that many studies have shown a beneficial effect to lowering cholesterol, and that despite the claims of some online health influencers, there are good reasons to believe that cholesterol plays at least some role in the formation of arterial plaque.
And that’s where an important clinical conundrum comes into play.
As Americans reduced their fat consumption in accordance with health advice throughout the 1970s, 80s, and 90s, rates of obesity and type two diabetes started to skyrocket. There are many possible explanations for this (it’s likely that more than one factor is at play), but by the early 2000s, a vocal minority of doctors began to suggest that perhaps as people cut back on their fat consumption, the resultant increase in refined carbohydrates was driving this new epidemic of “diabesity.”
Around this time, the Atkins diet – one of the more popular low-carb/high fat diets of the late 20th century – began to gain tremendous popularity. Dr. Atkins had published his first diet book in the early 1970s to great success, but the medical establishment had spent the ensuing 30 years trashing him and his diet as dangerous due to its high fat content and for a while it fell out of favor. Despite these warnings from health experts however, by the late 1990s patients “on the ground” were rediscovering that this diet worked very well for many of them.
It wasn’t until this time period (the early 2000s) that some scientists decided to finally test the Atkins diet out via experiments. Much to their surprise, the Atkins diet outperformed most other diets – at least in the short run – in terms of not only weight loss, but improvements in blood sugar, blood pressure, triglycerides, and HDL (“good”) cholesterol. And since that time, numerous studies have piled up with similar conclusions: when compared to low-fat diets, low-carb diets tend to perform at least as well and often better for all of these metrics.
As a result of this, today there are many low-carb diets – Atkins, Keto, South Beach, Paleo, Slow-carb, and more – that are followed by millions of people. Any primary care doctor, such as myself, has met more than a handful of people who have gone on one of these diets and experienced tremendous success in losing weight, feeling better, and improving a number of their blood markers. And the medical establishment has softened its stance on these diets, with many professional organizations now offering that a low-carb diet is a viable option for patients who are interested in weight loss or better metabolic health.
But there is one catch. Often – not always, but often – high fat/low carb diets such as the keto diet drive LDL cholesterol (the so-called “bad” cholesterol) way up. This continues to make many doctors – and patients – nervous.
What to do when faced with such a patient? They are happy on their diet, have lost weight, and have improved blood sugar, blood pressure, and triglycerides – all things that should reduce their risk for a cardiovascular event. But they also have a big spike in their LDL cholesterol, which per current thinking will increase their risk for a cardiovascular event. What is the net effect of all of this? Are they in grave danger from their spike in LDL, and hence should get off the diet? Or do the other benefits at least offset the LDL spike, such that they should continue the diet? Or, is it possible that in this one specific population of people, the LDL rise is not even a problem at all?
Until now, we’ve had no data at all to answer this question. As a result, this has become a very controversial topic in medicine.
Many doctors have continued to bash low-carb diets, or at least to urge caution in those low-carbers who see a big increase in LDL cholesterol, suggesting that such folks are substantially increasing their risk of someday suffering a cardiovascular event and should therefore get off the diet, regardless of what other benefits they may be experiencing. Others have tended to downplay this risk, noting that blood sugar, blood pressure, and abdominal obesity are much bigger risk factors for cardiovascular disease than LDL cholesterol, and so the rise in cholesterol is a worthwhile tradeoff for improving these markers. And some have even suggested that since all of our studies showing that high LDL is bad have been done in the general population – who are typically eating a mixed diet of fat, protein, and carbohydrates – the data might not even apply to low-carbers, who have in effect an untested metabolism that might be resistant to the harms of elevated LDL cholesterol. To date, no study has really looked at which of these groups is correct, which has left a lot of patients (and their doctors) in the lurch about the best course for those whose cholesterol spikes on a low-carb diet.
Enter Dave Feldman. By way of disclaimer, I have never met Dave and have no personal relationship with him, but I have been following his work for several years.
Dave is well known on the internet for his grass roots research into cholesterol. In brief, he’s a software engineer by training, who himself experienced massive benefits after going on a keto diet about 10 years ago – including weight loss, lower blood sugar, lower blood pressure, and a general sense of feeling better and more energetic. But he also developed a big spike in his LDL cholesterol. With his engineering background, Dave decided to look into this further before just abandoning his diet altogether. And slowly, through a series of experiments – first just on himself, then on other low-carbers who he met, and now finally (as I’ll explain in the next post) through an actual medical study that he’s crowd-funded – Dave has started to put together some data about this population of patients.
You can look Dave Feldman up if you are interested in learning more, and I will therefore not go into all of the details here. But in sum, Dave has really been interested in two questions: 1) WHY does LDL cholesterol go so high in some patients on a low-carb diet, and 2) HOW DANGEROUS is this rise in LDL?
In answer to the first question, Dave has put forward a new hypothesis called the “Lipid-Energy Model,” which (to simplify things) states that low-carbers often see a rise in cholesterol simply because their bodies are running on fat, and hence have to shuttle more fat around the bloodstream for fuel. Through a series of elegant experiments, Dave has accumulated some data suggesting that this may well be the case. Why would this matter? Because it may speak to the second question: if the rise in cholesterol experienced by low-carbers is due to a metabolically appropriate response, then perhaps their cholesterol behaves differently than the high cholesterol seen in the normal population, and may therefore be much less dangerous.
Which brings us to the second, and infinitely more interesting question: if you go on a keto diet and your cholesterol skyrockets as a result, is this a cause for concern? To answer that question, I will cover a study that Dave’s group recently published in more detail in my next post.
