Newsbites: Body mass index data; healthy eating and sleep; MIND diet for cognitive health
New Data on Body Mass Index (BMI)
Body Mass Index (BMI) is a ratio of weight to height. It has been used to group people as underweight, “normal” weight, overweight, or obese. While it is a useful public health tool, BMI’s ability to predict health risks on an individual level has recently been questioned.
An analysis of national health survey data concluded that a BMI in the “overweight” range (22.5 to 29.9 kg/m2) was not associated with a higher risk of death, especially in older adults.
The study analyzed data on over 554,000 adults with an average age of 46 years. Being underweight (BMI less than 18.5 kg/m2) or obese (30 kg/m2 or higher) was generally associated with higher risk of death in the nine to 20 years of followup. The relationship between overweight and risk of death, however, was inconsistent.
The authors concluded the clinical value of BMI on an individual level has limitations.
BMI does not account for differences between sexes and genders, across the lifecycle, and, importantly, across racial/ethnic groups. Body shape and composition vary among racial and ethnic groups. The BMI scale is based primarily on data collected from non- Hispanic White populations.
The American Medical Association (AMA) has concluded that BMI is an imperfect way to measure body fat and health risk. They suggest physicians use BMI in conjunction with other valid measures of risk, such as waist circumference, measurements of visceral (belly) fat, genetics, and metabolic factors.
You and your healthcare provider should not ignore your BMI, but it should be only one tool of many when determining risk for conditions like cardiovascular disease and type 2 diabetes (see page 4 for more information).
Eating a Healthy Diet Associated with Better Sleep
Adhering more closely to dietary guidelines was associated with lower incidence of problems falling asleep and staying asleep for women ages 68 to 73 living in Australia.
Of the nearly 8,000 participants, just over 70 percent reported having at least one symptom of sleep disturbance, and just over 20 percent had three to five symptoms. While overall adherence to dietary guidelines was poor, dietary intake closer to the guidelines was associated with fewer sleep disturbances.
The authors point out that this association goes both ways: high intake of energy-dense ‘junk’ foods have been associated with poorer sleep quality, and poor-quality sleep has been linked with increased intake of energy-dense foods.
Poor sleep is associated with increased risk of developing chronic conditions like high blood pressure, obesity, type 2 diabetes, cardiovascular disease, and, in older adults, depression and cognitive decline (particularly in women). Note that women who adhere to a healthier dietary pattern may have other characteristics that support better sleep, such as being physically active.
For Prevention of Cognitive Decline, Reduced Calorie MIND Diet Not Superior to Simply Cutting Calories
A randomized, controlled trial compared the impact on cognitive function of a MIND diet with mild caloric restriction to a typical diet with mild caloric restriction. The MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet emphasizes foods that have been associated with lower risk of dementia, such as leafy greens, berries, nuts, and olive oil.
Six hundred cognitively healthy, overweight or obese older adults with “suboptimal” diets and a family history of dementia were assigned to follow either the MIND diet or their regular diet, both with mild caloric restriction, for three years. The MIND diet group were given blueberries, nuts, and olive oil. Both groups received individualized dietary counseling. For the MIND-diet group, this counselling focused on shifting dietary intake to align with the prescribed dietary pattern, along with behavioral strategies to lose weight. The control group focused on calorie tracking, portion control, and behavioral strategies for weight loss.
The groups lost similar amounts of weight. Improvements in cognition were not statistically significant between the two groups and brain MRIs showed similar brain changes.
This study adds to the body of knowledge around dietary intake and brain health. When looking at these results, it’s important to consider that the controldiet group may have improved their dietary intake as they focused on losing weight, and the weight-loss itself may have positively impacted brain health in both groups. The MIND diet, like the Mediterranean and Dietary Approaches to Stop Hypertension (DASH) dietary patterns on which it is based, is an excellent choice for general health.
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