Posts Tagged ‘fat’

Myth Blown: Persons with Obesity Have Same Diet as Normal Weight

June 15th, 2011

One of the most pervasive beliefs about persons with obesity is that they eat an unhealthy diet and that persons of normal weight eat a healthy diet. Many, if not most, anti-obesity programs include teaching ‘healthy eating’ as part of their efforts to prevent and treat obesity. Ever since I started working in obesity in the late 1990s, I looked for evidence that the eating patterns of persons who were overweight or obese were different from those at normal weight. I was amazed that there was not any. I was even more amazed that many people  reacted with a “Why even ask?” attitude. They knew it was a given.

Hold on. New evidence indicates that  persons with obesity eat the same diet  as overweight and normal weight persons.

Jim Hill and colleagues looked at changes in consumption from NHANES in 1971-1975 to NHANES in 2005-2006. During this time, obesity increased dramatically. Carbohydrate consumption increased from 44% to 48.7%; fat decreased from 36.6% to 33.7% and protein decreased from 16.5% to 15.7%. But they, for the first time, could look at changes across BMI levels.

The percentage of energy from carbohydrates increased uniformly across both men and women across normal, overweight and obese groups. The percentage of energy from fat decreased uniformly across both men and women across normal, overweight and obese groups. Ditto, decreases in protein consumption. The authors note, “Furthermore, although the percentage of energy from fat has decreased, the total amount of fat consumer has not decreased in the setting of an overall increase in energy intake, primarily from carbohydrates. Even normal-weight men and women consume at least 33% of claories from fat, which could be considered a high-fat diet as absolute fat intake has not decreased but the proportion is smaller because of the overall increase in energy intake. The additional calories from carbohydrates combined with a high-fat diet may only further the propensity toward obesity.” Trends in carbohydrate, fat, and protein intakes a… [Am J Clin Nutr. 2011] – PubMed result

This finding has profound implications in terms of obesity policy. The assumption that obese people eat differently than the rest of the world is a powerful one which has gone unchallenged until now. Of course, this study does not address the quantity consumed nor consumption patterns on BMI levels above 30. Nevertheless, this study should spur researchers to take a closer look at this dietary pattern and its implications for policy.

Are we looking for answers in the wrong places?

January 23rd, 2010

In a cross-sectional and longitudinal study in Canada, nine known risk factors for overweight and obesity were examined. Only short-sleep duration, low dietary calcium intake and high disinhibited  eating were found to be significantly associated with higher BMI in both men and women. Short sleep duration had a greater effect than parental obesity, television viewing and physical inactivity. Population studies indicate that sleep duration has decreased over recent years. The authors note that affecting obesity by addressing  the traditional risk factors – reduced physical activity, high caloric intake and high fat intake – have not been very successful and that attention to factors which are not caloric per se may be worthwhile.  Risk factors for adult overweight and obesity in t… [Obesity (Silver Spring). 2009] – PubMed result

Downey Fact Sheet 5 – Measuring Obesity – The Body Mass Index

September 27th, 2009

pdficon_smallPrintable PDF

How do we know if one is overweight or obese?

There are several methods, but the one most frequently used by researchers and physicians is the Body Mass Index or BMI. The BMI is a mathematical formula involving dividing one’s weight (in kilograms) by one’s height in meters squared. The resulting number is one’s BMI. Thanks to the Internet, there are now a lot of calculators to do the math for us. This is just one of them. Calculate your BMI – Standard BMI Calculator . As you can see from the formula, the BMI is not adjusted for age, gender or other health status. It is meant to be a proxy for excess adipose tissue in the body. It does a pretty good job of that when studying a whole population or a subgroup. At the personal level, it may not be as good an indicator of excess adipose tissue. Waist circumference is sometimes used as an additional assessment of risk because it measures central adiposity, which is more likely to predict the risk for co-morbid conditions. (Generally, one BMI unit is equal to about 5 pounds.)

More sophisticated tools are sometimes used including hydrostatic weighing and DEXA which uses bioelectrical impedance to determine body composition.

The other problem with the BMI has to do with the cut-off points. In other words, what is the range for normal, overweight, obese and morbid obesity. Much research goes into evaluating what are the appropriate cutoffs. The studies are not always very clear…except for the fact that, at some point, increasing weight by any measurement means increased risk for comorbid conditions (See Health Effects) of mortality (See Obesity A to Z). A discussion of the needs for changes in BMI usage in the elderly is reported at An evidence-based assessment of federal guidelines…[Arch Intern Med. 2001] – PubMed Result

BMI may tell us a lot about populations but you might be interested in how your weight compares with others your age, race or gender. See: Average height and weight charts, men and women .

For many years, Americans were familiar with the Metropolitan Life Insurance Weight tables Height & Weight Tables. These tables are often used with patients considering bariatric surgery. Many surgeons discuss weight loss not in terms of BMI units but in terms of Excess Weight or one’s current weight minus the Metropolitan Life ‘ideal weight.’ Excess Weight Loss or EWL, then, becomes the standard to look at weight loss following bariatric surgery.ASMBS – Rationale for Surgery

The search for an improved BMI continues but it is well validated and continues to be used worldwide.

Read more: Pathophysiology of obesity. [Proc Nutr Soc. 2000] – PubMed Result

BMI Calculator Go to Calculate your BMI – Standard BMI Calculator

Background on US BMI criteria: Criteria for definition of overweight in transition: background and recommendations for the United States — Kuczmarski and Flegal 72 (5): 1074 — American Journal of Clinical Nutrition

Comparisons of percentage body fat, body mass inde…[Am J Clin Nutr. 2009] – PubMed Result

How does your weight compare to others of same race, gender and age? See:Average height and weight charts, men and women