Background
Death, taxes and headline news stories about the latest study questioning low carb diets are part of the predictable cycle of life. I have a recurrent calendar reminder set on my phone that warns me every 6-9 months that there will be such a story and my inbasket will be filled with messages such as the following one I received after the latest headline (shared with permission):
“Dr.Sinha, I’ve been following your book principles for the past 18 months and am happy to say that I lost 36 pounds, am no longer prediabetic and my triglycerides went from 356 mg/dL to 90 mg/dL…I also just signed up for my first half marathon this fall when I’ve been a lifelong couch potato. Despite me achieving these goals, I’m worried after reading all the headline stories like this one that says I might be shortening my life.”
-Arjun-
Let’s think about this for one moment. Because of a single headline news story, a gentleman that eliminated obesity, cured his prediabetes, normalized dangerously elevated triglycerides, and is now exercising at a level where he is able to sign up for a half marathon is now questioning if he may have shortened his lifespan.
This message in particular has motivated me to write a post I’ve been meaning to write for a long time, so every time the inevitable headline comes up and I get the anxious e-mails I can just say 4 words….”don’t worry, read this,” where the “this” will hyperlink to this post. So let’s dissect this study and others like it down to a few basic points.
Anatomy of a Nutrition Headline Story
Any time a nutrition headline story comes out, I ask you to do a few things and we’ll use the current study as an example.
1. Ignore Snap Judgments Based on Headlines
So your vegetarian sister-in-law who is a bit envious of the fact that you lost 20 pounds on a low carb diet, sent you a link from a “prestigious” news source with a compelling headline like the one below.
The goal of this attention-grabbing headline was not to inform you of a scientific breakthrough in an objective manner. The primary goal is to create a shocking and compelling headline that you will quickly skim over with your limited attention span, panic, and then proceed to share with everyone you know. The more you share the more they (publishers) earn.
2. Go Straight to the Source
Fortunately this particular news story did provide a direct link to the actual study, which is here, and comes from the prestigious medical journal, Lancet. Unfortunately even in the world of medical journal publications, “prestigious” does not mean scientifically accurate.
3. Go to the Methods Section
There are a few things you can see in the Methods section below which should already standout.
- Dietary questionnaire: The minute you see the word “dietary questionnaire” in a study, already become highly skeptical. This means that the study participants were asked to recall what they ate. I can barely recall what I ate yesterday, so know that any study that is putting it’s weight on the power of human recall, even if the study numbers are substantial like they are here, should be called into question. It has been shown that individuals filling out dietary questionnaires routinely underreport macronutrient intake like fat and carbohydrates.
- Check the Dates: When you read the latest headline, did you get the impression that this was cutting edge research observing a group of patients who are eating a healthy version of a lower carbohydrate diet like you? The questionable questionnaire was given to individuals between 1987-1989, which as of the writing of this post was over 30 years ago. To provide some context, this is when artists like Whitney Houston and U2 were at the top of the US Music charts.
Top Bollywood movies during that time, since I have so many Indian readers, were Mr.India, while US movies included Predator (starring my former California governor) and Robocop.
Perhaps this “latest study” doesn’t feel so cutting edge any more since it involved study subjects from a different era, and just think for a moment of what types of “low carb” diets people were consuming 30 years ago. Although they did 5 additional follow-up surveys with the last one in 2016-2017, a significant amount of the findings from this study are dependent on older, less reliable data.
This particular study type is known as a prospective observational study, where you start at some point in time (1987-1989 in this study) and “observe” the impact of a particular exposure, which in this case is diet and carbohydrate intake estimated using questionnaires, and then follow over time for associations with specific health conditions.
General rule of thumb is that nutrition observational studies are rife with flaws, inaccuracies and assumptions and should be taken with a large grain of salt (nutritional pun intended). Unfortunately it is expensive to run a more ideal study type, like a randomized control study, and the entities that can afford to finance such trials are big pharma companies who develop drugs. This is an excellent review article on some of the fundamental problems with nutrition studies.
The Fallacy of “Low Carb”
You cannot possibly classify human beings into comparable carb categories, since carb tolerance is highly individual. For a sedentary individual with insulin resistance, eating carbs north of roughly 150 grams daily is high carb since it’s often enough to trigger belly fat, high triglycerides, elevated blood glucose and other markers for increased diabetes and heart disease risk.
On the other hand, an athletic individual who is metabolically healthy with no signs of insulin resistance may be able to consume double the amount of carbs without adverse consequences, so the same 200g of carbs that is high carb for the first person can be normal carbs for the latter.
How do you know your own limits? You follow your markers of insulin resistance and body weight while also measuring your carbohydrate intake over time to see where you proper range is. I discuss this in great detail in my book and programs found here.
Food Quality and Sourcing Ignored
The other major problems in these nutrition observation studies is that food quality is completely ignored. Read the direct quote below in the conclusion section:
“Our findings suggest a negative long-term association between life expectancy and both low carbohydrate and high carbohydrate diets when food sources are not taken into account…”
We live in a world now where food sourcing sits at the heart of nearly every major nutritional movement. As a health practitioner I see the qualitative and quantitative results of what happens when patients eat better sources of plants, fish and meat and we are increasingly realizing the impact of chemicals found in foods that are not sourced properly containing an alarming amount of toxic, carcinogenic and hormonal effects.
This type of knowledge was largely ignored 30 years ago, so a typical low carb diet was more of a fast food diet with processed meats. Similar to a first generation Atkins diet where individuals shed body fat eating pounds of butter, cheese, bacon and red meat, with little regard for plants.
Study Conclusions
The important message from this study is that if you are eating a “low carb” diet, you must do it right. Don’t slip into that dangerous zone where all of a sudden your plate becomes dominated by animals, while plants get pushed aside. Always remember, plates should be filled with vegetables with a side of meat or fish, rather than the other way around.
The study also mentions that we should avoid either extreme (low carb or high carb) which makes sense, but again keep in mind that the definition of “low carb” varies for each individual and that number can also change for each individual. My patients who start off insulin resistant may have an upper tolerance limit of 50-60 grams of carbs, but after reversing their insulin resistance, improving their body composition and increasing their activity levels, they may be able to tolerate 2-3 times that much.
Again, use your weight and lab results to help guide you, and as I shared with the case study at the beginning, if those numbers are moving in the right direction through a balanced eating and lifestyle plan, I wouldn’t be distracted by the latest nutrition study based on unreliable questionnaires and old data.
The Future of Nutrition Studies
Fortunately we are now entering the realm of big data and more sensitive tools and technologies that can allow more reliable food tracking, alongside more convenient ways of assessing biometric results including gut and gene information. This type of data will help collect valuable evidence to determine the risks and benefits of different dietary approaches, while providing personalized nutrition recommendations, as is being done by 3T&AI, a company I’ve partnered with.
Also, check out the emerging studies by my friends at Virta Health that looks at the impact of the ketogenic diet on key cardiometabolic and diabetes parameters. Yes, these are short-term studies that need to be followed over time, but the impact on diabetes and additional cardiovascular risk markers is impressive and aligned with the results we see in our own clinic.
