Food for Thought: the Best Diets

by David Katz, M.D., Director, Yale Prevention Research Center

As you may know, U.S. News and World Report recently released a list of the “best diets” to accompany the rich harvest of weight loss resolutions for the New Year. It was my privilege to be selected one of the 22 judges.

As judges, we worked isolated from one another, so that none of us were privy to what the others might be thinking. In many ways, this is a positive, because our opinions were not prejudiced by each others’ passions or personal vexations. But it is also a negative for the very same reasons. Anyone who has seen the play or movie 12 Angry Men knows how powerful and beneficial a healthy exchange of ideas can be.

Notwithstanding, we handed in our reports independently. Each of us predicated our judgments of the 25 diets in seven different categories through the use of online materials, published papers and personal clinical experience. U.S. News and World Report submitted very useful summaries to us – which included links to recent and important research studies – but we were nevertheless encouraged to go beyond this material, something I am confident all the judges did.

My overall sense is that we agreed more than we disagreed, and that we were fairly comfortable with the majority of our conclusions. Having said that, the results represent the consensus of the panel and do not dovetail perfectly with my own worldview – nor, I suspect, with the worldview of any of my distinguished colleagues.

In the main, the rankings were a seal of approval for balanced, common-sense approaches to weight control. No diet based on a gimmick or sweeping distortions of a healthful dietary model scored well. Those diets that did score well were by and large conducive both to losing weight and achieving health. Top finishers included Weight Watchers, which came in first for both weight loss and ease of use, and DASH, a diet developed at the National Institutes for Health for blood pressure control that has since been shown to bestow other health benefits. The Mediterranean diet and the low-fat, plant-based diet developed by my friend and colleague Dean Ornish finished near the top as well.

Readers may note that different diets placed first for weight loss, health, diabetes and heart disease, respectively. To be honest, I find that a bit silly. Healthy weight loss is one of the most important ways of reducing the risk for heart disease and diabetes. A diet that reduces diabetes risk simultaneously reduces heart disease risk. Moreover, a diet that reduces the risk of diabetes and/or heart disease, two of the leading public health menaces of our era, is clearly beneficial for health. A diet cannot be good for health unless it lowers the risk of diabetes and heart disease. Axiomatically, diets that help prevent inflammation also fight diabetes, heart disease and many cancers.

I am confident you now can see where this all leads. A good diet is a good diet, full stop. A good diet helps to prevent chronic disease, control weight and promote overall health. A good diet is balanced, sensible, sustainable and enjoyable. And a good diet is suitable for the entire family so that while you are losing weight on the “____” diet, you don’t have to stop and wonder: “What in heck’s name are my kids eating?”

The same logical analysis can be extrapolated: from diet to foods to nutrients. Simply put, what’s healthy for us is healthy for us, and what isn’t, well … isn’t. Unfortunately, physicians – who throughout history have not been well trained in nutrition – have confused this issue pretty badly. For example, cardiologists have cautioned their hypertensive patients against sodium intake, while often overlooking the fact that an excess of sugar, starches and calories leading to weight gain will also cause blood pressure to rise. Diabetics have been warned about sugar, but they are at risk for hypertension and need to be careful about their sodium intake as well. Patients with high cholesterol have been advised to avoid trans fat, saturated fat, and dietary cholesterol – but excesses of salt and sugar can beget vascular injury as well.

It’s important to grasp that health cannot be achieved – and (with the exception of deficiency syndromes) disease cannot be avoided – on a nutrient-by-nutrient basis. What truly matters is the overall nutritional quality of a food. Broccoli is not immensely nutritious because it is free of trans fat; broccoli is immensely nutritious because it is broccoli!

And, obviously, a diet is made up of foods. A top quality diet is made up of top quality foods. And there is, indeed, evidence – in 100,000 people – that such healthy dietary patterns are associated with not only weight control but better health overall: less diabetes, less cardiovascular disease, and lower risk of dying prematurely of any cause.

So it’s clear that we can, and should, establish some logical parameters for evaluating the quality of a diet. We can, and have, devised metrics specific to that goal – with newer and better ones always evolving. But can we actually say which diet is “the best”?

I have opined on this topic before, and basically said – “No.” We have ample evidence to support a basic concept of healthful eating, and almost none to say which of the several realistic contenders (Asian, Vegan, Mediterranean, etc.) is truly the best. The logistics of a once-and-for-all trial to tell us which diet is truly best (if indeed one is) are sufficiently difficult that we may confidently forecast doing without such evidence for the longer term. After all, would you be willing to be randomly assigned to eat a Mediterranean diet, a Vegan diet or a Paleolithic diet for the next 25 to 30 years? Unless a whole lot of folks answer “yes,” the trial we need to definitively answer the question cannot take place.

In some ways, that’s a good thing, because it means that while we do have a very well-substantiated, evidence-based framework of healthful eating – one that is conducive to weight control, chronic disease prevention and vitality – we are left with considerable room for modification to that theme. There is benefit in such doubt, because it makes way for customization and the indulgence of your personal preferences and priorities. You are the boss, as well you should be.

But let’s be clear, there IS a theme – and though you are in charge, you abandon the theme at your likely peril, at least in the long term. The basics of the theme have been articulated by Michael Pollan as well as by anyone: “Eat food, not too much, mostly plants.”

Eating food means REAL food. Pronounceable food. If it glows in the dark, you probably shouldn’t consume it. A good rule of thumb is: the longer the shelf life of a product, the shorter the shelf life of the person eating the product. Out just today (January the 9th, 2012) is a paper suggesting that eating real food reduces the risk of ADHD in our children, while highly-adulterated foods have the opposite effect. Science, meet intuition!

“Not too much” might seem like difficult advice to accept, but quality control provides for quantity control. Many processed foods are of the “No one can eat just one” variety – and specifically engineered to be that way. Wholesome foods – an apple, for instance – are of the “No one wants to eat more than one” variety. In fact, I’ve recently learned about a mother who lost 115 lbs. due almost entirely to her use of the NuVal system in her supermarket. She simply traded up to more nutritious choices in each aisle. By addressing quality, quantity and weight pretty much took care of themselves.

“Mostly plants” is pretty self-explanatory. An emphasis on plant foods is evident in almost all diets that succeed at both weight control and health, and is, as a bonus, important for the health of the planet. At the end of the day, being slim and healthy won’t count for much if we don’t still have a viable planet to call our own.

As noted previously, Weight Watchers won the top prize in several of U.S. News and World Report’s categories: best for weight loss, best commercial program and easiest/most convenient to use. I am an advocate for Weight Watchers because their program clearly succeeds for weight loss (on the U.S.N.W.R. site, each diet now has statistics attached to it, and those individuals reporting success with Weight Watchers outnumber those who do not by two to one; the ratio is the opposite for every other diet on the site!), is sensibly aligned with healthful eating and provides the structural support many individuals require.

I believe, nevertheless, that we can do even better – through building skill power systematically and comprehensively to facilitate lifelong health and weight control, while satisfying the needs of all family members simultaneously. A program called Weigh Forward that I helped develop is a good example of this. I also see opportunities for customizing variations on the topic of weight control based on genetic testing, particularly for those persons who are unusually weight loss resistant. This is an idea that is just now ripening into real applicability.

As we appraise the best diets at the start of a new year, we can celebrate the winners – but still regret that too many out there are still losing. A majority of adults in the United States are overweight or obese – as our far too many of our children. Our best efforts to date are still not good enough.

What would be ideal is modifying the world so that eating well and being active were behaviors shared by all. While waiting for that change – or even better, while working towards it – the best diet is framed by considerations of not just losing weight, but obtaining health; not just you, but your family; not just now, but for all your life. Within the boundaries of that theme, there is plenty of latitude for you to be in charge, and to choose the best path ahead for yourself and your family. Outside of those boundaries is a whole world of misleading claims and potential hurt. Therefore, the 21 other judges and I encourage you to stay inside the lines.

(published March 29, 2012)

David L. Katz MD, MPH, FACPM, FACP is the founding director of Yale University’s Prevention Research Center. He is a board certified specialist in both Internal Medicine and Preventive Medicine/Public Health. Known internationally for expertise in nutrition, weight management, and chronic disease prevention, as well as integrative care and patient-centered care models, Katz is active in patient care, research, teaching, and public health practice. His website is DavidKatzMD.com.