A Nutritionist’s Perspective
First, a quick preamble. This is the first in what I hope will be a series of posts on food and nutrition. This essay was adopted and updated from a talk I gave three years ago on my campus at Appalachian State University in Boone, NC. I had great help from my graduate student at the time, Drew Hilton, in preparing this material.
I want to talk about diets and some of the problems with undertaking one to lose weight. To make this more interesting and applicable I have decided to discuss three popular diets and to draw lessons from them that can be applied to all diets. The diets I have chosen are generally considered fad diets and are not generally recommended by dietitians. That will heighten the lessons we can draw. I will try to be objective about the pros and cons of these diets.
A word of caution here. I am not a Registered Dietitian, nor do I pretend to be able to prescribe specific foods and diets to specific people. I am an expert in the biochemistry of nutrition and metabolism, and I tend to see diets from that perspective. So, let’s get started.
I have chosen three diets to draw lessons from, the paleo diet, the keto diet, and the gluten-free diet. Many people would call these “fad diets” because they tend to be out of favor with nutritional experts and their popularity waxes and wanes, but they still remain popular with many people today. We will address them one at a time. My goals here are not to discredit every diet out there or completely discourage you from undertaking a diet if you need. I hope to give some sensible advice riffing off these diets that many of my readers have already tried.First though, why are so many people dieting? America has been in an obesity epidemic for about the last 70 years. And we have seen the consequences in rising cases of diabetes and hypertension and many other chronic diseases. People are constantly worried about their weight. About 43% of teenage girls admit to being recently on a diet. Dieting is a $43 billion industry with videos, supplements, books, mail order foods, and medications for dieters. A search for “diet books” on Amazon brings up 60,000 hits. Recent research showed that half of all diet advertisements had at least one false claim. Here is one of my favorites. And for all of that, only about 5% of dieters are successful in keeping the weight off.
The Paleo Diet
The paleo diet is a diet loosely based on what our paleolithic ancestors may have eaten. It eliminates dairy, grains, sugar, legumes, processed oils, salt, alcohol, coffee, and most processed foods. There was growing interest in the 80s and 90s, but Loren Cordain’s book The Paleo Diet in 2002 established the diet as a national phenomenon. The rationale is that we are evolutionarily adapted best to a diet prior to the development of agriculture in the Neolithic age. Hence, agriculturally developed foods such as grains, dairy and sugar are discouraged on this diet. If we return to this diet we will avoid the modern degenerative diseases- heart disease, diabetes, and cancers. Characteristics of an ideal paleo diet include higher protein, lower carbs, higher fiber, higher unsaturated fats, higher potassium, alkaline load, and higher vitamins, minerals, antioxidants, and phytochemicals. Prohibited foods include cereal grains, legumes, dairy, refined sugar, potatoes, processed foods, refined vegetable oils, and salt. Promoted foods include grass-fed /free-range meats, fruits and vegetables, fish/seafood, eggs, nuts/seeds, and healthful oils (olive, walnut, avocado, coconut, etc.). Obviously, the paleo diet tends to cost more than the usual western diet.
Here are some of the errors that I see in the philosophy underpinning the paleo diet. We have a rather rudimentary understanding of what paleolithic people ate, but what we know for sure is that by that time humans were all over the world and eating all kinds of foods. There is no single paleolithic diet. Another wrong assumption is that the human genome has not changed or evolved since then and since the advent of agriculture. One simple counterexample is the advent of lactose tolerance in some folks, allowing for the common practice of drinking milk. This probably came about in more than one place by a genetic mutation about 10,000 years ago. Also erroneous is the simple assumption that the foods our ancestors ate are the same ones available in the supermarket. What our ancestors might have called “corn” or “carrots” bear almost no resemblance to those products today. A true paleo diet would be almost inedible to the modern consumer. Finally, the paleo adherent gives no credit to the marvelously flexible human digestive physiology. Consider all the diets that currently exist around the world that humans thrive on. We are truly a wonderfully omnivorous and adaptive species that seems to be able to do rather well on almost any diet. My apologies here to my dietitian friends who are cringing at the thought of all their well-crafted dietary recommendations being subverted.
All that said, I’m not suggesting that you will die a short terrible death on the paleo diet. Let’s take a quick look at some scientific studies. There aren’t many of these, but we can draw some conclusions. In a study titled, “Long-term effects of a Palaeolithic-type diet in obese postmenopausal women: a 2-year randomized trial”, the researchers ran a trial in which they trained half of the subjects to prepare a paleo diet and half a healthy control diet. They concluded that, “A Palaeolithic-type diet has greater beneficial effects vs a [control diet] regarding fat mass, abdominal obesity and triglyceride levels in obese postmenopausal women.” In another more comprehensive study titled “Paleolithic nutrition for metabolic syndrome: systematic review and meta-analysis” the authors summarized the results from four studies, “The Paleolithic diet resulted in greater short-term improvements in metabolic syndrome components than did guideline-based control diets.”
So, these studies support the benefits of the paleo diet as a weight loss diet that improves our lab numbers. While this is encouraging for paleo enthusiasts, it is not surprising. Restrictive diets tend to result in weight loss. Also, diets that can decrease hunger pains are also helpful. We know that foods higher in protein and fats tend to be satiating, meaning the eater feels full longer. This diet and the keto diet both are higher in protein and fat than the normal western diet. If I suggested a diet to you that removed all grains that began with the letters W and S and all vegetables and fruits and began with C and G, you would lose weight, if only because you would spend half your day in the grocery store, trying to figure out what not to eat. The question I would pose to purveyors of these diets is whether the success is in the story they tell or the restrictions they impose.
Secondly, almost any diet that results in weight loss almost invariably results in improved metabolic scores. This often puzzles the critics. How can a high fat diet result in lower blood cholesterol levels or lower blood pressure? It happens because the high fat diet is more satiating and results in weight loss that results in healthier cholesterol and blood pressure.
So, is the paleo diet safe? Three thoughts. Safe compared to what diet? First of all, we know that the standard American diet, shared by many around the world, is not exactly the epitome of perfect nutrition. For starters, it has too much sugar, not enough fiber, is low in some key minerals and has way too much salt. So, compared to that diet, many diets are better. But compared to a healthy vegetarian diet, I would vote for the veggies. Two, at what weight? One topic I am not addressing here is who should be on a diet and why. It would be (and might be someday) a topic for a series of blogs. Let me say simply that the risks associated with obesity go up with weight and the benefits of weight loss and being on any diet that works go up with weight. For normal weight folks, I would take you back to the faulty assumptions and the numerous restrictions and ask you to consider a more enjoyable and healthier alternative. Finally, consider the cost. For the extra cost you are giving up beans, beer, and bread.
The Keto Diet
Having covered some of the common issues, these next two diets will go more quickly. First is an issue with names. The original ketogenic diet was a true medical diet that was quite extreme, with up to 90% of energy coming from fat and protein compared to the usual 50%. It was used successfully to treat children with refractory epilepsy. The so-called “Keto Diet” in modern use is nowhere near that in proportions. Most keto diets are low-carbohydrate diets with about 20-30% compared to the usual 50-60% carbs. The most famous of these diets is the Atkin’s Diet, named after the famous doctor who invented it.
These diets are very popular and much scientific research has been published on them. One major study titled “Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: a meta-analysis of randomized controlled trials” summarized 13 clinical trials of 12 months or longer. They found, “Overall, 37% dropout rate. Average 37% carbs, Keto diet had 0.91 kg greater weight loss, lower triglycerides, diastolic BP, and LDL and higher HDL.” Several points to make here. There is always a high dropout rate from weight loss studies. Weight loss is hard and keeping people in the studies is hard. Note the high carbs at 37%. This is not all that restrictive. Note the marginal benefit of 0.91 kg, about 2 lbs for the keto groups. The benefits to triglycerides, blood pressure, LDL, and HDL, were equally small.
The physiology of the keto diet is intriguing and deserves some attention. The basic idea is that if we can lower the incoming carbohydrates, then we can lower the blood glucose levels. This will have specific benefits for people tending towards or in diabetes. If the body gets low in blood glucose, which it absolutely needs to fuel the brain, then it has a backup system called ketogenesis. In ketogenesis a group of metabolites call ketone-bodies can be produced from fats when sugars, like glucose, are in low supply. Keto enthusiasts will emphasize at this point that burning up fat is what dieting is all about, so this state called ketosis and being fueled by ketone bodies is a good state to be in. But the body still sees it as an emergency state, not the preferred state. As an analogy, imagine working in a building where the fire alarm was sounding about half the time.
Is the keto diet safe? Three concerns. Based on the physiology I just described, certain folks should be concerned. Folks who can run into super low blood glucose levels should beware of this diet. That would include folks with diabetes who are on glucose controlling drugs such as insulin. These ketone bodies, in high enough concentration can be acidic. There is a small risk of ketoacidosis. This takes us back to the original definition of the keto diet and the question of just how restrictive of carbs the diet is. With moderate carbs at 30-40%, there is going to be little ketosis. At low carbs of 10-20%, ketosis will be frequent. When ketones are high and glucose is low, the brain says, “Hungry.” This doesn’t sound all that pleasant. So, what is the quality of life here, especially given the increased cost again, and the restrictive diet. Remember, no doughnuts, drinks, or Doritos. As stated before, any benefits we see from this diet are more than likely due to the restrictions that lead to modest weight loss that lead to healthier lab numbers.
Gluten is a protein in 3 grains: wheat, barley, and rye. It is also found in processed foods such as soy sauce, salad dressing, food starch, beer, etc.. The diet was first developed for people with celiac disease, an autoimmune disease that affects the intestine and slowly blocks absorption of nutrients. Untreated leads to death from malnutrition. Here is an interesting full disclosure for my readers. I have celiac disease. I have been diagnosed for about 12 years. While there are inconveniences to be sure, it is one of the least troublesome autoimmune diseases to have.
The fad diet we know today largely developed in the early 21st century with books Grain Brain and Wheat Belly, condemning wheat and other grains as bad for health. People started diagnosing themselves with “non-celiac gluten sensitivity” and popularizing gluten-free diets for many health benefits. The medical profession has been puzzled by this new condition and has slowly recognized it. Gluten-free products are now a $15 billion food industry.
There is now a cross-over between gluten-sensitivity and the FODMAP diet and Crohn’s disease and irritable bowel syndrome. Common symptoms include abdominal pain, bloating, and gas. This is a very complex topic. Suffice it to say that Crohn’s and irritable bowel are both mystifying intestinal conditions that are difficult to treat and may be diet related and may be related to the carbohydrates in the diet. Gluten may be mixed up in there somewhere. Others have suggested gluten-free diets as possible cures for schizophrenia, fibromyalgia, and endometriosis. These have been largely disproven.
Gluten-free diets have not been taken up as often as the other diets for weight-loss. To the extent that they have and to the extent that studies have followed up, it appears that the results follow our previously established wisdom that restricting a diet for any reason often means less calories, which generally means weight loss and improved number. But if you are restricting wheat, you must imagine a diet that restricts donuts, cakes, and most office treats. Imagining losing weight on that diet is not too hard.
Please allow me just a minute to elaborate on the common errors found in the popular book Wheat Belly. Many of the benefits of eliminating wheat are due to weight loss, not to some toxic properties of wheat. The book has many testimonials, but few clinical trial results. While the author will point to the dangers of various constituents of foods, none of the dangerous properties were unique to wheat starches or proteins. The author claims that dramatic changes to the gluten content of wheat varieties has happened over time, especially since the Green Revolution of the 50s and 60s. However, recent research has clearly shown that no changes in wheat composition has occurred. The connections between a large number of diseases and wheat are completely unproven.
Here are some concerns that nutritionists have about gluten-free products currently on the market. They tend to be lower in fiber than their glutenous alternatives. They are not necessarily fortified with B vitamins and iron. They often contain more salt, fat, and sugar. They tend to be more than two times as expensive.
We have seen some common threads through these three diets. Let me summarize those for you here:
- Most fad diets won’t hurt in the short-term.
- Most diet benefits come from restrictions that lead to weight loss.
- Long-term adherence is hard and may not be as helpful as one would like.
- They are almost always more expensive.
If these three diets are not recommended in the long-term, what makes a good diet? Here are some common-sense suggestions:
- One you can stay on for a lifetime
- That is balanced and minimally restrictive
- That lowers metabolic syndrome and other disease risk factors
- That moderates weight slowly
Best Diet Advice from author Michael Pollan
My favorite food and nutrition author is actually not a nutritionist. He is a journalist who has written several thoughtful books on the subject. At the end of one of his books he give this advise for a good diet.
- Eat (whole) foods
- Not too much
- Mostly from plants
2 thoughts on “Paleo, Keto, and Gluten-free Diets”
Excellent article for all readers.
Wonderful article Dr Root. Love Micheal Pollan.