by Marion Nestle

Currently browsing posts about: Calories

Oct 29 2012

Why isn’t USDA keeping up its series on calories in the food supply?

In November 2011, I wrote about my frustration over the USDA’s discontinuation of a data set it had published continuously since 1909: Nutrients in the Food Supply.   For unfathomable (to me) reasons, USDA stopped the data set in 2006.

For decades—since 1909—USDA has converted information about food availability (the amount of food produced in the U.S., less exports, plus imports) to per capita nutrient availability in a continuous series (it also publishes data on calorie intakes from certain foods). 

This is the data set I use to explain how calories in the food supply have increased to today’s 3,900 per person per day from 3200 in 1980—an increase of 700 calories per day in parallel with rising rates of obesity.

USDA stopped this series in 2006. It now only publishes calorie supply figures that have been adjusted for waste. 

When I wrote USDA to ask whether more recent data were available, here’s what I got back (in its entirety):

Because of other project priorities the Food Supply project has been curtailed.  There are programming issues to which we haven’t been able to devote available resources.

In July this year, I wrote letters to everyone I could think of at USDA who might shed some light on this and, hopefully, restore the data set.  Although I hated to bother her, I even wrote to Deputy Secretary Kathleen Merrigan.

Her reply: 

 As I will discuss in a later post this week about USDA’s data on sugar availability, the agency seems to be changing the way it evaluates food supply data. 

This is bizarre.  USDA must have figures on total calories available in the food supply.  Otherwise, how could it produce figures adjusted for waste? 

I’ve been concerned that I’m the only one who cares about this, but a similar issue has emerged about USDA data on sugar availability.  I’ll write about that once hurricane Sandy blows over.

Oct 19 2012

Calories as an instrument of government control?

My 2012 book with Mal Nesheim, Why Calories Count: From Science to Politics, includes a chapter on the use of calories in international relations.

I thought of this chapter while reading a story in yesterday’s New York Times.

Apparently, the Israeli military restricted the amount of food available to residents of Gaza during the blockade that lasted from from 2007 to mid-2010.

The Israeli military calculated the number of calories that the blockaded residents would need to avoid malnutrition.

The purpose of the blockade was to weaken support for Hamas, the militant group that won legislative elections in 2006 and took full control of Gaza in 2007 after a brief factional war…In the calculation, Israel applied an average daily requirement of 2,279 calories per person, in line with World Health Organization guidelines.

I’m not sure where the 2,279 figure comes from.  Calorie estimations established jointly by the Food and Agriculture Organization and the World Health Organization say that adult men aged 20-70 need 2400 to 3000 calories a day on average, depending on age, weight, and physical activity level.  Adult women need 1800 to 2400.

The FAO sets a calorie cut point for populations to define hunger.  It defines populations consuming 1,800 calories per capita per day, on average, as chronically undernourished and hungry.

On this basis, 2,279 will be adequate for some adults—those who are female, smaller, older, and less active.  It is unlikely to be adequate for younger, bigger, more active men.

The Israeli Defense Ministry released this document under a court order.  It would be interesting to see how it arrived at this figure.

For an interesting discussion of the use of calories as an instrument of state power, see Nick Cullather’s “The Hungry World: America’s Cold War Battle against Poverty in Asia.”

 

Sep 21 2012

Nova: Is a calorie a calorie?

Mal Nesheim and I have just written a piece for Nova Science Now, based on our book, Why Calories Count: From Science to Politics.

Is a Calorie a Calorie?

By Malden Nesheim and Marion Nestle

Ever since the 19th century, nutritionists and the general public have accepted the “calorie” as the unit of choice for describing the energy content of food. Yet some scientists still debate whether all food calories are the same.

Do calories from a chocolate bar, for example, have the same effect on your waistline as the same number of calories from an orange? Putting it another way—and getting to a oft-invoked question in the debate—will you be more successful losing weight with calories from a low-fat diet than with the same number of calories from a low-carbohydrate diet? Or might the reverse be true? (As protein typically occurs in low amounts in foods—10 to 15 percent in the average diet—a low-fat diet is necessarily a high-carb diet, and vice versa.)

To read the rest of it and see how Nova illustrated it, click here.

Aug 30 2012

Does starvation increase longevity? Not in monkeys.

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.

Aug 5 2012

Low carb or low fat: Do calories count?

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

 

 

Jul 30 2012

Pizza chains want easier (or no) menu labeling

Now that the Supreme Court says that the Affordable Care Act is constitutional, it’s time to get those pesky menu labeling regulations in place.  That Act, you may recall, included a provision to take menu labeling national.

Late in May, Nation’s Restaurant News reported that pizza restaurant chains were banding together to fight FDA’s forthcoming menu-labeling regulations.

The American Pizza Community (TAPC) represents chains like Domino’s Pizza, Papa John’s Pizza, Little Caesar Enterprises, the International Pizza Hut Franchise Holders Association, Hungry Howie’s and Godfather’s Pizza.

TAPC members want alternatives for menu labeling that “would work for pizza.”

When there are 34 million ways to top a pizza just at Domino’s, it’s easy to understand how the one-size-fits-all situation currently proposed doesn’t work for pizza.

On June 4, Food Chemical News said the pizza industry would be asking Congress for an exemption from the menu labeling final rule.

Two days later, TAPC denied that charge.

On June 19, the Washington Post reported that TAPC met with congressional representatives to push for changes to the menu labeling plan.  What kind of changes?  Could they include exemptions?  Not clear.

TAPC is getting somewhere.  Congressman John Carter (R-TX) has just introduced a bill to weaken the national menu labeling law.  This would exempt supermarkets and convenience stores from having to post calorie information on prepared foods, gives a break to pizza, and allows calories to be listed by serving size.

Also in the meantime, Food Chemical News says the House Appropriations subcommittee told the FDA to narrow the focus of its menu labeling rule.  Translation: leave out movie theaters and, maybe, pizza.

I happen to love pizza, but it is unquestionably a major source of calories in American diets.  A slice of a big thick pizza can easily run 1000 calories.  I’d like to think that some pizza eaters might find that information useful.

I think pizza places should label calories—really, they can figure out how to do it—and that’s what I told  CBS TV on June 20.

Margo Wootan at Center for Science in the Public Interest (CSPI) has an op-ed in The Hill with a good summary of the reasons why menu labeling needs to get moving.  If you agree, CSPI has a model letter you can quickly send to the President, the Secretary of Health and Human Services (the FDA’s parent agency), and the FDA.

What’s holding up the regs?  First, the Supreme Court, but that’s no longer an excuse.  The upcoming election maybe?  That’s no excuse either.

Jul 23 2012

New data on calories reported as consumed

USDA has just released the latest figures on nutrient intakes among Americans.  These amounts are reported by a statistically determined sample of people interviewed as part of the What We Eat in America NHANES—the National Health and Nutrition Examination Survey.

Having just published Why Calories Count: From Science to Politics, I’m interested in calories.

The survey results from 2009-2010 for calories per day for adults over the age of 20:

  •  Men          2512
  • Women     1778

How many of those calories are consumed away from home?

  • Men         35%
  • Women   30%

How are daily calories distributed?

No, the percentages do not add up to 100%.  That’s because of snacks.  What percent of calories is consumed as snacks?

  • Men       24%
  • Women 23%

No surprises here, but the figures are fun to play with.

Compared to the figures reported in Why Calories Count for 2008, the figures for daily intake are not significantly changed.

Note: These are reported figures, and remain well below the 3000 calories a day for men and 2400 for women observed in studies that actually measure calorie balance.

Jun 27 2012

Does where calories come from matter to weight maintenance? A new study says yes, but I’m skeptical.

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

DIETS CARB% FAT% PROTEIN% DECREASE IN TOTAL ENERGY EXPENDITURE, Calories/Day
Weight-loss 45 30 25  Not reported
Low-fat (high-carb) 60 20 20 ~400
Low-Glycemic Index 40 40 20 ~300
Very low carb (high-fat) 10 60 30 ~100

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.
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