Obesity is defined as an excess of body fat. Body mass index, or BMI, is a ratio of weight to height and is commonly used for screening for obesity. Epidemiological and observational studies have shown that BMI provides an approximation of total body fat for most individuals, and it is used to define different weight groups in terms of risk for obesity-related conditions.
For adults (20 years and older), a BMI of less than 18.5 is considered underweight, 18.5 to 24.9 as normal weight, 25 to 29.9 as overweight, and greater than or equal to 30 as obese. Factors such as age, sex, ethnicity and muscle mass can influence the relationship between BMI and body fat. BMI does not distinguish between excess fat, muscle or bone mass, nor does it provide any indication of the distribution of fat among individuals.
For older adults, there has been some research suggesting a protective effect in individuals with certain health conditions and an overweight or obese BMI; however, further research is needed regarding the effect of obesity on mortality in this population. The 2014 Clinical Quality Measures from the Centers for Medicare & Medicaid Services indicate a BMI > 23 and < 30 for adults 65 years and older should be used for screening purposes. Weights falling outside of that "normal parameter" would need to be documented and routinely monitored.
According to the "Food and Nutrition for the Older Adult Guideline" by the Academy's Evidence Analysis Library, multiple assessment indicators (which includes BMI) should be used for classifying overweight/obesity in older adults, regardless of their age. Obtaining a weight history and inquiring about any recent weight changes during a nutrition assessment, the initial step in the Nutrition Care Process, will aid in this evaluation.
Some older adult clients may have a target or usual weight that does not correlate with any equation or table. The important issue is achieving a stable weight for a period of 6 months or more. Usual Body Weight, an individual's weight throughout adult life or a stable weight over time is the preferred standard for older adults. Any recent weight changes, especially unintentional weight loss, would also need to be addressed in a care plan.
The Hamwi formula used for individuals over 5 feet tall is sometimes used as a simple tool for quickly estimating desirable body weight or ideal body weight; however it does not account for usual body weight which is considered more appropriate for weight-related interventions in older adults.
- Men: 106 + 6 lb for every inch over 60 in.
- Women: 100 + 5 lb for every inch over 60 in.
- Add 10% if person has large frame, subtract 10% if person has small frame.
A comprehensive nutrition assessment requires the ability to observe, interpret, analyze and infer data to diagnose weight-related nutrition problems. Additional factors for the registered dietitian nutritionist to consider regarding weight management for an older adult would include the client's physical and cognitive abilities, any co-morbidities, their personal choice and unique preferences, as well as quality of life.
- Centers for Disease Control and Prevention. Body Mass Index: Considerations for Practitioners. Accessed May 19, 2021.
- Dorner B, Friedrich EK. Position of the Academy of Nutrition and Dietetics: Individualized Nutrition Approaches for Older Adults: Long-Term Care, Post-Acute Care, and Other Settings. J Acad Nutr Diet. 2018 Apr;118(4):724-735.
- Nutrition Care of the Older Adult: A Handbook for Nutrition throughout the Continuum of Care. Dietetics in Health Care Communities DPG, Marla Carlson, Kathleen C. Niedert, PhD, RDN, CSG, LD, FADA.
- Centers for Medicare & Medicaid Services. 2014 Clinical Quality Measures (CQMs) Adult Recommended Core Measures. Preventive Care and Screening: Body Mass Index (BMI) Screening and Follow-Up. Accessed May 19, 2021.
- Academy of Nutrition and Dietetics Evidence Analysis Library. "For the assessment of overweight/obesity in older adults, what is the effect of weight change on physical function and mortality?" Accessed May 18, 2021.
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