Currently browsing posts about: Diets

The New York Times front page today has a report of a long-term study at NIH of severe calorie restriction in Rhesus monkeys.  It found that calorie restriction did not extend the monkeys’ lifespan.

I’m not at all surprised.  My co-author and I reviewed the literature on calorie restriction for a chapter in our book, Why Calories Count.

The new study makes news because it contradicts a study done in Wisconsin showing that severe calorie restriction extends life.  Severe means 25% to 30% fewer calories per day that are needed to maintain normal body weight.  I’d call this a starvation diet.

An editorial accompanying the report of the study in Nature attributes the difference between the results of this NIH trial and the Wisconsin study to a difference in dietary composition, suggesting that calories differ in their effects.

Not necessarily.  The Wisconsin study allowed the control monkeys to eat a lot of junk food and they were fatter than normal.  The NIH study restricted calorie intake in its control monkeys so they maintained normal weight and were healthier.  This is the simplest explanation of the difference.

Studies in rats, mice, and many other animals show that calorie restriction extends life.

But what about primates?

Starvation can hardly be good for health.  It causes weight loss, of course, but also a host of physiological and psychological problems.  These were extensively documented in humans during World War II in Ancel Keys’ Starvation studies.

The relationship between BMI and human longevity has been examined in several recent studies, all of which show similar results: Longevity is best associated with BMIs in the range considered normal or slightly overweight.  Above that range—but also below it—mortality increases.  

Being underweight is associated with higher mortality.

A Canadian study provides this example:

And one from the National Cancer Institute provides another:

The bottom line?  Eat a healthy diet and balance calories to maintain a healthy weight within that range.

I’ve been sent a copy of the Department of State’s Diplomatic Culinary Partnership Initiative. called “Setting the Table for Diplomacy.”

Its mission statement:

The Diplomatic Culinary Partnerships initiative builds on Secretary of State Hillary Rodham Clinton’s vision of “smart power” diplomacy, which embraces the use of a full range of diplomatic tools, by utilizing food, hospitality and the dining experience as ways to enhance how formal diplomacy is conducted, cultivating cultural understanding and strengthening bilateral relationships through the shared experience of food.

I particularly like the idea of “using food as a foundation for public diplomacy programs to learn about different cultures and discuss important related issues such as nutrition, sustainability and food security.”

Yes!

Everybody eats.  This is my kind of diplomacy.

Here’s my once a month on the first Sunday Food Matters column for the San Francisco Chronicle, out today:

Nutrition and public policy expert Marion Nestle answers readers’ questions in this column written exclusively for The Chronicle. E-mail your questions to food@sfchronicle.com, with “Marion Nestle” in the subject line.

Q: I’m confused about calories. If I cut calories to lose weight, does it matter what foods I eat? Or are all calories the same?

A: As the co-author of “Why Calories Count: From Science to Politics,” I hear this question all the time.

The short answer: Calories matter for weight. The choice of foods that provide the calories matters a lot for health and may make it easier for you to diet successfully.

To lose weight, reducing calorie intake below expenditure works every time.

To prove this point, a professor at Kansas State University lost 27 pounds in 10 weeks on the Twinkies diet – one Twinkies every three hours with occasional snacks of chips, sugary cereals and cookies. Even so, he cut his usual calorie intake by 800 a day. Anyone would lose weight doing that.

Only four dietary components provide calories: fat (9 per gram), carbohydrate and protein (4 per gram each) – and alcohol (7 per gram).

Does the particular mix of these components make any difference to weight loss? Yes, say proponents of diets low in carbohydrate, especially rapidly absorbable sugars and refined starches.

Low-carbohydrate diets are necessarily high in fat, and somewhat higher in protein. Do people lose weight on them because of the effects of carbohydrates on insulin levels or because low-carbohydrate diets help reduce calories?

This question does not have an easy answer, but not for lack of trying. Weight-loss studies are hard to do. Estimating calorie intake is notoriously inaccurate, and measuring calories is difficult and expensive.

The first measurement study I know of took place in 1964. Investigators from the Oakland Institute for Medical Research studied weight loss in five obese patients in a hospital metabolic ward. They calculated the number of calories needed to induce rapid weight loss in each patient, and fed each of them a liquid formula diet containing that number every day. Every few weeks, they changed the formula to vary the proportions of protein (ranging from 14 percent to 36 percent of calories), fat (12 percent to 83 percent), and carbohydrate (3 percent to 64 percent).

Regardless of the proportions, all patients lost weight at a constant rate. The investigators titled their study “Calories Do Count.”

This study was conducted under rigidly controlled conditions of hospitalization and involved actual measurements – not estimations – of calorie intake and body weight.

But what about weight-loss studies involving people who are not incarcerated? Since the early 2000s, numerous clinical trials have shown low-carbohydrate diets to produce greater weight loss than low-fat diets. Some also have observed improvements in blood pressure, blood glucose levels and blood lipids.

But it is so inaccurate to estimate calorie intake in such studies that most didn’t bother to try. This means they can’t say whether the weight loss was due to composition of the diet or to calorie reduction.

It’s possible that low-carbohydrate, high-fat diets make people less hungry, but the evidence for this is mixed. Most studies of extreme diets of any type report high dropout rates or failure to stick to the diet for more than six months or so. And even though initial weight loss is rapid on low-carbohydrate diets because of water loss, these diets are low in fiber and some vitamins.

One problem with losing weight is that it takes fewer calories to maintain smaller bodies. Dieting also reduces energy expenditure.

One recent study of that problem involved taking detailed measurements for several years, and illustrates the difficulties of obtaining definitive answers to questions about diet composition and energy balance.

The researchers wanted to know whether diet composition affected energy expenditure in very obese people who had just dieted off up to 15 percent of their weight. They found that a low-carbohydrate diet did not slow down energy expenditure nearly as much as a low-fat diet, meaning that low-carbohydrate diets might make it easier for people to maintain weight loss.

On this basis, the investigators said, “The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective.”

Perhaps, but study subjects were fed prepared calorie-controlled diets for only four weeks, and lost and maintained weight under highly controlled conditions. Does diet composition matter for weight maintenance in the real world? Longer-term studies by other investigators show that diet composition makes little difference in the ability to maintain weight loss.

Most reviews of the subject conclude that any diet will lead to weight loss if it cuts calories sufficiently.

Obviously, some diets are better for health than others.

Face it. The greatest challenge in dieting is to figure out how to eat less – and to eat healthfully on a regular basis – in the midst of today’s “eat more” food environment. And that’s a much more important research problem than whether low-carbohydrate or low-fat diets work better for weight loss.

Marion Nestle is an author and a professor in the nutrition, food studies and public health department at New York University. She blogs at foodpolitics.com. E-mail: food@sfchronicle.com

As the co-author of a recent book called Why Calories Count: From Science to Politics, I am well aware of how difficult it is to lose weight.

The problem

• When you are dieting and losing weight, you require fewer calories to maintain and move your smaller body, and your metabolism and muscle activity—and, therefore, your total energy expenditure–slow down.
• To maintain the weight loss, you need to eat less than you did before you began dieting.

But what would happen if you could adjust your diet to keep your energy expenditure from slowing down?

Enter Ebbeling et al in JAMA, with a comprehensive study to address precisely that question.  The results of the study and editorial comments on the findings demonstrate how complicated and difficult it is to obtain definitive answers to questions about diet composition and calorie balance.

• The investigators asked whether calorie-controlled diets containing varying amounts of carbohydrate, fat, and protein, and varying in glycemic load (a measure of rapidly absorbable carbohydrates in foods) affected total energy expenditure in obese people who had just lost 10% to 15% of their weight, but were still obese.
• They found that the diet lowest in carbohydrate did not slow down energy expenditure as much as did the low-glycemic index diet, or the one lowest in fat.
• They concluded: “The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective.”

This study took years and involved a very large number of state-of-the-art physiological measurements.

But I want to focus on the question of whether calories from all sources are metabolically equivalent.   Here’s my understanding of the study.

The methods

Ebbeling et al started by offering $2500 to obese volunteers to participate in a 7-month weight-loss trial.   In my view, the 21 subjects who finished the study worked hard for that money.

They had to participate sequentially in a:

• Weight-monitoring phase for 4 weeks, during which they ate their typical diets while the investigators monitored their weight.
• Weight-loss phase for 12 weeks, during which they were fed pre-prepared diets calculated to contain about 60% of their usual calorie intake so they would lose about 2 pounds a week.  The average weight loss over 12 weeks was an impressive 14.3 kg (31.5 pounds).
• Weight-stabilization phase for 4 weeks, during which they were fed pre-prepared diets that provided the reduced number of calories needed to maintain their newly reduced weights.
• Testing phase of 4 weeks on each of three pre-prepared test diets (total: 12 weeks).  All three test diets provided the number of calories needed to maintain the reduced weight.  During each of the 3 testing periods, investigators measured—not estimated—the subjects’ total daily energy expenditure (resting metabolism plus activity).

The composition of the diets

Note that whenever one component of a diet gets changed, the other two components change too.   Because protein usually occurs in foods in relatively low amounts, a low-fat diet is necessarily a high-carbohydrate diet, and vice versa.

The results

• The weight-loss part of this study showed that when overweight people were allowed to eat only calorie-controlled pre-prepared diets, they lost weight quickly and maintained the weight loss.
• The test-diet part of the study showed that the diet lowest in carbohydrate (and, therefore, highest in fat) had the least effect in slowing down total energy expenditure.   The diet that slowed down overall energy expenditure the most was the one lowest in fat.

If these results are correct, people eating high-fat, low-carbohydrate diets are likely to have the easiest time maintaining weight loss.  In contrast, people on low-fat, high-carbohydrate diets are likely to have a harder time maintaining weight loss.

But does this mean that calories from different sources have different effects on metabolism?  Proponents of the Atkins (high-fat, low carb) diet say yes, according to an account in USA Today (in which I am also quoted).

I’m still skeptical.  The subjects in this study lost and maintained weight under highly controlled, calorie-restricted conditions, in which the calories came from a relatively low-fat, moderate-carbohydrate, high-protein diet (average diets contain 10% to 15% protein).

The accompanying editorial notes that heat losses are greater for protein than for carbohydrate or fat, and also raises questions about whether physical activity declined more with the low-fat (high-carb) diet than the others.  It also notes:

Each diet was consumed for only 4 weeks. A weight stabilization protocol…may not have adequately accounted for changing energy needs associated with readjustment to new diets.

These provocative results…emphasize the current incomplete knowledge base regarding the importance of dietary macronutrients and energy expenditure, especially after weight loss.

Under the relatively short, highly controlled feeding conditions of this study, the composition of the diet may indeed matter to metabolism.  But does diet composition matter for weight maintenance in the real world?

Other longer term studies of “free-living” people out and about in their communities show little difference in weight loss or maintenance between one kind of diet and another.

More research needed!

The bottom line

• If you want to lose weight, eat less (it worked well for the subjects in this study).
• It may help to avoid excessive consumption of sugars and easily absorbed carbohydrates.
• Once you’ve lost weight, adjust your calorie intake to maintain the weight loss.
• And understand that science has no easy answers to the weight-loss problem.

Paul Kindstedt, Cheese and Culture: A History of Cheese and its Place in Western Civilization, Chelsea Green, 2012.
Kindstedt, a professor of food science at the University of Vermont and co-director of its Institute for Artisan Cheese, has organized his history by time period and region, from the Paleolithic origins of cheese to current attempts to regulate raw milk.  His material is well referenced and the book is full of facts and observations that will delight cheese lovers.

Seamus Mullen, Hero Food: How Cooking with Delicious Things Can Make Us Feel Better, Andrews McNeel, 2012.

I don’t usually blurb cookbooks but I couldn’t resist this one from Seamus  Mullen, the chef-owner of Tertulia in lower Manhattan.

This gorgeous book proves without a doubt the point I’ve been making for years: healthy food is delicious!  Take a look at what Seamus Mullen does with vegetables, fruit, grains and everything else he cooks.  I can’t wait to try his 10 Things to Do with Corn.  His food can’t guarantee health, but will surely make anyone happy!

On Tuesdays, I answer questions about nutrition in NYU’s student newspaper, the Washington Square News.  Today’s is about youthful immortality.

Question: Many students have expressed that, being so young, they can eat whatever they want and stay thin. What kind of implications does the type of food we eat have on our body weight? If a student is thin but eats bad foods, are there still detrimental effects? Additionally, at what age does what you eat tend to have the biggest effect on you?
Answer: It’s not only youth that keeps college students trim. It’s the lifestyle: running to classes, late nights studying or partying, irregular meals, eating on the run. Once students get past the hurdle of the “freshman 15” — the weight gain that comes from unlimited access to meal plans — most do not gain weight in college.

It’s what happens afterward that counts. Even the most interesting jobs can require long hours in front of a computer or chained to a desk. Eating out of boredom becomes routine and, once middle age hits, it’s all over. The metabolic rate drops with age, and you can’t eat the same way you used to without putting on pounds.

The college years are a great time to start behaving in ways that will promote lifetime health. If you smoke cigarettes, stop while you can. Don’t binge drink. Practice safe sex.

As for diet, eat your veggies. Whenever you can, eat real foods, shop at farmers’ markets and learn to cook. Cooking is a skill that will bring you — and your family and friends — great pleasure throughout life. If you cook, you will always have the most delicious and healthiest of diets at your fingertips.

You don’t know how? Try an Internet search for “free cooking lessons online.” Mark Bittman’s Minimalist videos, for example, make things simple with results that can be spectacular.

Do the best you can to eat well now, and think of it as easy life insurance.

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!

This semester I answer students questions about nutrition on Tuesdays in the student-run Washington Square News.  Today’s is about fiber.

Question: We tweeted and linked to the article you were cited in The New York Times on Tuesday, and you mentioned the importance of fiber in a diet. How much fiber is good to have in a daily diet, and what does it do for our bodies? What are good sources of fiber — cereal bars, granola bars? How much is too much fiber?