Currently browsing posts about: Diet-and-dieting

The New York Times asked me, among others, to contribute to its  Room for Debate blog on the question of whether anyone could possibly need to hear one more word about what constitutes a healthful diet.  Here’s my two-cents’ worth:

Better Information and Better Options

Of course Americans need more information about eating well. Otherwise we wouldn’t have an obesity problem. In my daily teaching and contact with the public, I hear endless confusion about what to eat.

People are bombarded with conflicting advice, much of it from sources with a vested interest in selling particular foods, supplements or diet plans. Nutrition studies tend to focus on single nutrients, making their results difficult to apply to real diets. No wonder people have a hard time knowing what or whom to believe.

This is too bad, really. The basic principles of healthy eating could not be easier to understand: eat plenty of vegetables and fruits, balance calorie intake with expenditure, and don’t eat too much junk food.

If such principles seem hard to follow, it is surely because of how they affect the food industry. Balancing calorie intake often means eating less, but doing so is bad for business. Food companies must do everything they can to sell more food, not less.

So they make foods available everywhere — even in drug, book and clothing stores — and in very large portions. Few people can resist eating tasty food when it’s right in front of them. Large portions alone explain rising rates of obesity: they encourage people to eat more calories but to underestimate what they have eaten.

Healthy eating requires a food environment that makes it easier for everyone to make better choices. It also requires a food system that makes it cheaper to buy fruits and vegetables than less healthful foods, so everyone can afford to eat healthfully. Fix the farm bill!

A new diet study just out from the American Journal of Clinical Nutrition went to a lot of trouble to prove the obvious.  When it comes to weight loss, how much you eat matters more than the proportion of fat, carbohydrate, and protein in your foods.

Researchers at the Pennington Biomedical Research Center got volunteers to eat diets that were supposed to differ in proportions of fat (40% vs 20%), carbohydrates (35% vs. 65%), and protein (25% vs. 15%).

The results of the study are consistent with the findings from many previous studies:

• The major predictor for weight loss was adherence to the diet.
• People on all of the diets lost weight by six months, but regained some of it by two years.
• The study had a high drop-out rate (hence the importance of adherence).
• It was hard for people to stick to the diets, especially those at the extremes of one dietary component or another.

In my book with Malden Nesheim coming out on April 1, Why Calories Count: From Science to Politics, we review the previous studies of whether what you eat matters more to weight loss than how much you eat.

Some people find it easier to stick to diets that are higher in protein and fat.  I’m guessing that proponents of low-carbohydrate diets will argue that none of the diets in this particular study was really low in carbohydrate.

But studies show that people have a hard time adhering to diets that are very low in carbohydrate.  The low range in this study—35%—is at the lower end of acceptability for many people.

The bottom line: all diets work if you stick to them.

While everyone is arguing about the effect of high and low protein diets on weight gain, US News has come out with another one of its rankings, this time on diets.

The committee of experts advising US News ranked diets basically on the basis of ease of use, taste, flexibility, and effectiveness. They advised against diets that are too restrictive, require or eliminate certain foods, or are otherwise difficult to follow.

They ranked Weight Watchers #1 as the best weight-loss diet:

Dieters can eat whatever they want as long as they don’t exceed their allotted daily points. No foods are forbidden, occasional treats are encouraged, and the plan emphasizes all-you-can-eat fresh fruits and veggies. Experts liked the optional weekly meetings, since support is crucial to compliance. They also applauded Weight Watchers for being realistic, flexible, and filling. It scored more than a full star above the average in this category and was crowned the easiest diet to follow.

Weight-loss diets must do two things: restrict calories, and provide balanced nutrient intake.  As we explain in Why Calories Count: From Science to Politics (publication date April 1), this boils down to “eat less” and “eat better.”

Diets have to allow you to eat foods you love (in moderation, of course).

Food is a great source of pleasure and many of us live to eat.  Not being able to eat the way we used to is one of the great tragedies of getting older.  Alas!

To the extent that any diet plan helps you eat less, eat better, and enjoy what you are eating, it ought to work.

I was intrigued by the new study from the Pennington Research Center concluding that weight gain depends on calories, not how much protein you eat.

The idea that the protein, fat, or carbohydrate content of your diet matters more to weight than how many calories you eat persists despite much evidence to the contrary.

This study did something impressive.  It measured what people ate, how much they ate, and how much energy they expended under tightly controlled conditions.

This is unusual.  Most studies of weight gain and loss depend on participants’ self reports.

Measuring is much more accurate, as I discuss in my forthcoming book with Malden Nesheim, Why Calories Count: From Science to Politics (out April 1).  If you want calorie balance studies to be accurate, you have to measure and control what goes in and out.  The Pennington is one of the few laboratories in the country that can do this.

Pennington researchers got 25 brave people to agree to be imprisoned in a metabolic ward for the 12 weeks of the study.  The volunteers had to eat nearly 1,000 extra calories a day over and above what they needed to maintain weight.  Their diets contained either 5%, 15%, or 25% of calories from protein.

All of the volunteers gained weight (no surprise), although the low-protein group gained the least.  Most of the weight ended up as body fat.  The medium- and high-protein groups also gained muscle mass.  The low-protein group lost muscle mass.

All of the differences in weight gain among individuals could be accounted for by energy expenditure, either as activity or heat (protein causes higher heat losses).

The Wall Street Journal (January 4) did a terrific summary of the results:

This tells you that low-protein diets cause losses in muscle mass (not a good idea), and that there isn’t much difference between diets containing 15% protein (the usual percentage) and higher levels.

The study also suggests that higher protein diets won’t help you lose weight—unless they also help you cut calories.  That calories matter most in weight gain and loss is consistent with other studies based on measurements, not estimations.

Of course the quality of the diet also matters: it’s easier to cut calories if you are eating plenty of vegetables, fruits, whole grains and a varied diet based largely on relatively unprocessed foods—and it’s harder to gain weight on such diets.

Reading the New York Times dining section this morning kicked up my annoyance at use of the term “protein” to refer to meat.  A story about what to do with holiday leftovers says “…repurposing top-quality proteins into dinner is easier than it seems.”

Another on Simon Doonan’s new book, Gay Men Don’t Get Fat, quotes him as pointing out that “straight food…tends to be leaden, full of protein, thick with fat.” Now you know.

But protein is a nutrient.  Foods are sources of nutrients.

Nutritionists like me consider protein a “macronutrient,” meaning that foods contain many grams of protein and also that protein is a source of calories (4 per gram as opposed to 9 for fat and 4 or so for carbohydrate).

Diets contain about 15% of calories from protein on average, an amount much greater than most people need—about twice the minimum required for maintenance and growth.

“Protein” is most definitely not a synonym for meat or even tofu (see table).  I’ve listed the plant sources of protein in Italics.

FOOD SOURCES OF PROTEIN IN U.S. DIETS

Source: J Am Diet Assoc. 2010 February ; 110(2): 291–295.

Grains, vegetables, and fruits are not the biggest sources, but they are important contributors.  Vegans, who consume no animal products at all, do not lack for protein.

And while proteins from meat resemble our own proteins more than do proteins from vegetables, their constituent amino acids are the same in all foods.  Varying food intake and eating enough food takes care of amino acid balance.

Hence, my peevishness at the use of “Protein” as a separate category in USDA’s MyPlate (see previous post).

Grains and dairy, each with its own sector, are important sources of protein in American diets.

Why protein?  USDA used to call the group “meat” even though it contained beans, poultry, and fish.  The meat industry ought to be happy about “protein.”  Meat producers have spent years trying to convince Americans to equate meat with protein.

A plea: let’s keep terms clear and talk about nutrients when we mean nutrients and foods when we mean foods.  Protein is not food.

NOTE: More about protein tomorrow when I discuss the new JAMA study on whether high-protein diets help you lose weight (spoiler alert: they don’t).

U.S. News has just released its rankings of 20 popular diet plans—the “Best Diets for Healthy Eating.”

The top five:

• DASH (Dietary Approaches to Stop Hypertension)
• TLC (Therapeutic Lifestyle Changes)
• Mediterranean
• Mayo Clinic
• Volumetrics

These may be healthy, but from the standpoint of survey respondents, they don’t work very well.  To the question “Did this diet work for you?” the “no’s” hugely outnumber the “yes’s” for a whopping 16 of the 20 diets.

The four exceptions:

• Weight Watchers (#6)
• Vegetarian Diet (#9)
• Eco-Atkins (#15)
• Vegan (#16)

Diets are about maintaining or losing weight.  This means balancing food energy against the amount of energy used in metabolism and activity.   To lose weight, you have to eat less or move more or do both.  It also helps to eat better and make healthier food choices.

All of the diets on the US News list are based on healthy food choices.  But these are the only four diets on the list that seem to help a majority of people to eat better and eat less.

The latest issue of JAMA has a paper on a “portfolio” of dietary means to reduce blood cholesterol levels.

The paper is likely to get lots of press because it concludes that consuming the “portfolio”—a combination of plant sterols, soy protein, viscous fibers, and nuts—does a better job of lowering LDL-cholesterol (the “bad” kind) than does dietary advice to reduce saturated fat.

The paper is unusually difficult to read  (see the Abstract, for example).  But besides that, I interpret the study in part as a drug trial.

One look at the Abstract and I immediately suspected that this study must have been sponsored by a maker of plant sterol margarines.

Bingo!

Plant sterols are well established to reduce blood cholesterol levels.  Unilever, which makes Take Control margarines, is one of the sponsors.

As I interpret it, the study shows:

• Advising people who weigh an average of 76 kg (167 pounds) to consume a healthy diet doesn’t work.  Study subjects did not change their diets by much during the six months of the trial.  No news here.
• Advising people to add things to their diets has a better chance of succeeding than advising taking things away (like saturated fat).
• All of the portfolio items have been established to lower blood cholesterol in clinical trials, although the evidence for soy protein seems a bit iffy these days.
• The study does not distinguish between the relative effects of soy protein, fiber, or cholesterol lowering margarines. If soy is eliminated, that leaves fiber and margarines. I’m guessing the margarines were the critical factor. Hence: a partial drug trial.

And because my book on calories is coming out next March, I must point out that the study groups reported losing  losing small amounts of weight, which means they must also have reduced their calorie intake.  Weight loss alone should help with blood cholesterol.

The take-home message: if you really do substitute nuts, sources of fiber, and healthy foods for whatever less healthful foods you used to eat, you ought to get some health benefit, with or without plant sterol margarines.

QED: Healthy diets produce health benefits.

It’s always nice to see that confirmed.

I’m in the midst of working on the copy-edited manuscript of my forthcoming book with Malden Nesheim Why Calories Count: From Science to Politics (University of California Press, March 2012) and spending every minute I have on it.  So I’m going to take some shortcuts on the blog this week and deal with some questions I’ve been asked recently.

One is right on the topic of the book:

Q.  Could you address the 2,000 calorie a day number (both its history and speculate on how an individual can arrive at a more personalized amount)? Short of metabolic testing (and I read conflicting opinions on that, too), it seems rather difficult to figure out how much I should be eating.

A.  Nothing could be easier, and here’s a preview of the kind of thing that will be in this book (with footnotes, of course):

If you look at  a food label, you will see ingredient contents compared to a 2,000-calorie average diet: “Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.”

Here’s the history of where that came from:

The FDA wanted consumers to be able to compare the amounts of saturated fat and sodium to the maximum amounts recommended for a day’s intake—the Daily Values.  Because the allowable limits would vary according to the number of calories consumed, the FDA needed benchmarks for average calorie consumption, even though calorie requirements vary according to body size and other individual characteristics.

From USDA food consumption surveys of that era, the FDA knew that women typically reported consuming 1,600 to 2,200 calories a day, men 2,000 to 3,000, and children 1,800 to 2,500. But stating ranges on food labels would take up too much space and did not seem particularly helpful. The FDA proposed using a single standard of daily calorie intake—2,350 calories per day, based on USDA survey data. The agency requested public comments on this proposal and on alternative figures: 2,000, 2,300, and 2,400 calories per day.

Despite the observable fact that 2,350 calories per day is below the average requirements for either men or women obtained from doubly labeled water experiments, most of the people who responded to the comments judged the proposed benchmark too high. Nutrition educators worried that it would encourage overconsumption, be irrelevant to women who consume fewer calories, and permit overstatement of acceptable levels of “eat less” nutrients such as saturated fat and sodium. Instead, they proposed 2,000 calories as:

• consistent with widely used food plans
• close to the calorie requirements for postmenopausal women, the population group most prone to weight gain
• a reasonably rounded-down value from 2,350 calories
• easier to use than 2,350 and, therefore, a better tool for nutrition education

Whether a rounding down of nearly 20 percent is reasonable or not, the FDA ultimately viewed these arguments as persuasive. It agreed that 2,000 calories per day would be more likely to make it clear that people needed to tailor dietary recommendations to their own diets. The FDA wanted people to understand that they must adjust calorie intake according to age, sex, activity, and life stage. It addressed the adjustment problem by requiring the percent Daily Value footnote on food labels for diets of 2,000 and 2,500 calories per day, the range of average values reported in dietary intake surveys.

 As to how many calories you personally need, I think they are too difficult for most people to count accurately to bother.  The bottom line: If you are eating too many, you will be gaining weight.   

The best advice I can give is to get a scale and use it.  If your weight starts creeping up, you have to eat less.

The book will go into far more explanation of such issues but for that you will have to wait until March.