Is your cardiologist making you fat?

When you study human nutrition, two things quickly become obvious. The first is that we don’t really understand much about human nutrition. The second is that, despite not understanding much, we have to decide we should eat every day. Some of us even go around telling others what they should eat. The wise may preface their advice with an admission of our collective ignorance, but most of us have nutritional opinions that are as passionately defended as they are unfounded.

In fairness, there has been a lot of nutrition research, but those studies “prove” things that are contradictory. Eggs are bad for you; eggs are good for you. Fish is the healthiest thing you can eat; eating fish will give you heavy metal poisoning. For the average person, this is enough to make us throw our hands up and say “OK, just pass the donuts please.” 

Most nutrition data is based on flawed epidemiological surveys. A scientist will ask people questions like “Over the past year, how many salads have you consumed?” How would you answer that question now? 50? 100? 300? Would whatever number you came up with be more than a stab in the dark? Mine wouldn’t, and as a health coach I spend a lot of time thinking about diet and nutrition. 

Because you don’t know (you can’t possibly know) how many salads you ate, how you answer the question is influenced by how you understand yourself. If you think “I’m a healthy person who eats salads,” you will answer the question with a higher number than will the person who thinks “I’m not bothered about my health and I only eat salad when I feel like it.” Those two people could in fact have been eating the exact same number of salads in a year, but one is more inclined to overestimate and the other to underestimate numbers that can never be more than an educated guess. 

For these reasons and more epidemiology has limited value in answering the question “What’s behind the obesity crisis?” So let’s consider another set of tools: mechanistic explanations.

Mechanistic explanations of obesity come in various forms, the most simplistic of which is the caloric surplus model. The obesity epidemic, proponents of this explanation claim, is caused by overeating. To reverse it, all must “eat less and move more”. 

There is no observation that is so obviously true and so obviously unhelpful. If the question is, “Why are more prone to obesity now than at any time in our history?”, “because we’re eating more,” sounds like an answer that a pedantic child would give. Obviously we’re eating more, but it’s not like our ancestors never overate. Why are we consistently eating a lot more and in ways that don’t seem to nourish us and often leave us hungry? The “calories in, calories out” explanation fails to adequately explain the nature of our current problems.

More sophisticated mechanistic explanations involve hormones. Ghrelin is a hormone that makes us hungry; insulin, even at fairly low levels, prevents fat cells from releasing fat into the blood stream; leptin makes us feel full; glucagon tells the body to release energy from its fat stores. Surely the obesity epidemic has something to do with dysfunction in these hormones. This kind of mechanistic explanation, I would suggest, is where we must find definitive answers.

In this context let’s talk about cardiology. Before I get to the negative, let me first say that cardiologists provide a valuable service and if I ever have a heart attack I hope that I’m in the care of a good cardiologist. 

But cardiologists have an obsession that may have unfortunate implications when it comes to obesity and health overall: lowering LDL cholesterol. Since the 1960s we’ve understood that replacing dietary saturated fat with dietary unsaturated fat – in particular linoleic acid – significantly lowers blood serum cholesterol levels. Linoleic acid is an Omega 6 Poly-unsaturated fatty acid (PUFA) that is found in seed oils like soy oil, corn oil and canola oil. In some studies, for example the Minnesota Coronary Experiment which took place from 1968-1973, linoleic acid consumption was closely linked with a significant drop in LDL cholesterol levels. That study and others like it drove a huge cultural shift. Traditional animal fats – butter and lard were common in the West, but for many of us the list includes ghee and beef tallow – were out. Seed oils like corn, canola and soy oil were in. Other foods known to raise cholesterol like eggs and shellfish were also demonized.

There’s a key problem with the Minnesota Coronary Experiment and similar studies: the scientists didn’t publish all of their results. We now know, thanks to the work of some good investigative journalists, that the participants who were able to lower their cholesterol saw no benefits. They were as likely to die of a heart attack and slightly more likely to die of all causes than those who didn’t lower their cholesterol. As Dr. John Abramson of Harvard is reported to have said, “Dying with corrected cholesterol is not a successful outcome.” So these studies, though highly influential, did not correlate low cholesterol levels with better results.

Despite the dodgy science, these studies were very successful in influencing dietary guidelines in the US and around the world and in changing public perceptions around healthy and unhealthy food. Margarine made of transfats and skim milk were staple foods when I was growing up in the 1980s. My grandmother was made fun of for her “old fashioned” insistence on cooking with ghee, while the rest of us made traditional daals and biryanis with soybean oil, an ingredient that wasn’t even around when these recipes were invented generations ago. 

Eating more seed oil may be one reason that obesity rates are rising. This study found that linoleic acid intake was an independent risk factor for mice developing insulin resistance and obesity. Biochemically speaking, there are reasons that excess linoleic acid consumption might make our bodies more insulin resistant and therefore more prone to developing obesity and type 2 diabetes. Those reasons have to do with how our bodies process and burn different fatty acids for energy. These explanations – like explanations that blame excess carbohydrate consumption – rely on the relationship between our food and our hormones to explain why those who eat diets full of processed foods are more likely to be obese and unhealthy.

Others have written at length about the biochemistry and there are some great podcasts that go into the details. This one with Dr. Paul Saladino may be a good place to start. And Peter Dobromylskyj from Hyperlipid is the first one who proposed that your cardiologist might be making you obese (full credit to him for the title of this blog post).

But at the very beginning of this blog post I wrote that the first thing to understand about nutrition is that we don’t understand very much. I think that’s probably true even in the examples I’m talking about. Those who argue that corn oil is healthy will cite a lack of studies in human populations testing the impact of dietary linoleic acid on obesity, as well as data that seems to indicate that when people take carbs out of their diet and replace those carbs with fat – even fat from corn oil – those people tend to get healthier. I think the critics are right. I can’t say categorically that your cardiologist is making you fat. I don’t have all the evidence to back up that statement, or at least I don’t have it yet. But the cardiologist doesn’t either. 

Which brings me to a third, and for me the most useful approach. Epidemiology is limited, we don’t fully understand the biomechanics as yet, but we can learn from history. You and I and all of our families and friends are living proof of millions of years of evolution that has made us into what we are today. I don’t know that what my ancestors were eating was the optimal diet for humans, but I know that it was pretty good. If it hadn’t been, I wouldn’t be here. I also know that generations ago cancer and heart disease were unheard of in my family, but now those diseases seem to be everywhere. Contrary to popular opinion this isn’t because we now live longer; gains in average life expectancy have to do with reductions in childhood and infant mortality, not anything relating to old age. That to me is good enough evidence to look at the foods that we’ve introduced in recent years and ask whether we might have been better sticking to our more traditional foods. 

For many of us, those traditional foods included a fair amount of carbohydrate and even processed carbohydrate. My ancestors have been milling grains and making flatbreads for thousands of years. Those who’ve worked with me will know that I often suggest low-carb diets as an efficient way to lose weight, balance blood sugars and heal a number of disorders. These insights doesn’t necessarily change that; for many people low-carb diets are still going to be the best therapeutic option. 

But history suggests that the carbs may not be the underlying cause of the metabolic dysfunction we see everywhere in modern societies. It may be the cardiologist’s advice.