Weight loss can decrease dementia risk and improve mental performance and infertility.
The Effects of Obesity on Dementia, Brain Function, and Fertility
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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
In the ABCs of health consequences of obesity, if A is for Arthritis, and B is for Back Pain and Blood Pressure, C is for Cancer, and D is Diabetes, then E is for Encephalopathy.
Encephalopathy means brain disease. There’s consistent data linking obesity in middle age to higher risk of dementia later in life. Overweight individuals have about a third higher risk, and those who are obese in mid-life seem to have about 90 percent greater risk of becoming demented. The risk isn’t just limited to future dysfunction, though. People with excess body weight don’t appear to think as clearly at any age.
Obese individuals show broad impairments in what are called executive functions of the brain, such as working memory, decision-making, planning, cognitive flexibility, and verbal fluency. These “play a critical role in everyday life.”
People may think about their obesity and the resulting stigma they experience as much as five times an hour, but the cognitive deficits do not appear to arise just from distraction; there are structural brain differences between normal weight and overweight individuals.
A review entitled “Does the brain shrink as the waist expands?” noted gray matter atrophy across all ages among those carrying excess body fat. This reduced brain volume has then been correlated with the lower executive function. Compromised integrity of the rest of the brain—the white matter—suggests accelerated brain aging, even in young adults and children with obesity. Cognitive deficits in young populations suggest it’s something about the obesity itself that’s affecting brain function, rather than a later clinical consequence, such as high blood pressure. Purported mechanisms for this executive dysfunction include obesity-related inflammation and oxidative stress.
So, does weight loss improve cognitive function? Based on a meta-analysis of 20 studies, mental performance across a variety of domains can be significantly improved with even modest weight loss; though no studies have yet to be done to determine if this then translates into a normalization of Alzheimer’s disease risk.
F is for Fertility, or rather failed fertility. Overweight couples struggling to have children “should be educated on the detrimental effects of fatness,” one meta-analysis concluded, as weight loss is associated with an improvement in pregnancy rates among infertile women. Men also may suffer impaired fertility. The heavier a man is, the greater their risk of having a low sperm count or being completely sterile. This may in part be due to the effects of excess body fat on testosterone levels.
Fat isn’t just the primary site of estrogen production in postmenopausal women, but in men as well. There’s an enzyme in body fat that actually converts testosterone into estrogen. Men even going from obese to just overweight could potentially raise testosterone levels in their blood 13 percent.
A more dramatic cause of infertility in obese men is called “hidden penis.” Also referred to in the medical literature as buried penis, concealed penis, or inconspicuous penis, it occurs when excess fat in the pubic area subsumes the male member (since the base is attached internally to the pubic bone). It’s also called trapped penis, because the moist enfolding skin surfaces can result in a chronic inflammatory dermatitis leading to scarring, requiring a surgical intervention. So, “F” may also stand for Free Willy.
Please consider volunteering to help out on the site.
- Pedditzi E, Peters R, Beckett N. The risk of overweight/obesity in mid-life and late life for the development of dementia: a systematic review and meta-analysis of longitudinal studies. Age Ageing. 2016;45(1):14-21.
- Loef M, Walach H. Midlife obesity and dementia: meta-analysis and adjusted forecast of dementia prevalence in the United States and China. Obesity (Silver Spring). 2013;21(1):E51-5.
- Yang Y, Shields GS, Guo C, Liu Y. Executive function performance in obesity and overweight individuals: a meta-analysis and review. Neurosci Biobehav Rev. 2018;84:225-44.
- McCrady-Spitzer SK, Levine JA. Nonexercise activity thermogenesis: a way forward to treat the worldwide obesity epidemic. Surg Obes Relat Dis. 2012;8(5):501-6.
- Willette AA, Kapogiannis D. Does the brain shrink as the waist expands? Ageing Res Rev. 2015;20:86-97.
- Walther K, Birdsill AC, Glisky EL, Ryan L. Structural brain differences and cognitive functioning related to body mass index in older females. Hum Brain Mapp. 2010;31(7):1052-64.
- Kullmann S, Schweizer F, Veit R, Fritsche A, Preissl H. Compromised white matter integrity in obesity. Obes Rev. 2015;16(4):273-81.
- Veronese N, Facchini S, Stubbs B, et al. Weight loss is associated with improvements in cognitive function among overweight and obese people: a systematic review and meta-analysis. Neurosci Biobehav Rev. 2017;72:87-94.
- Best D, Avenell A, Bhattacharya S. How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence. Hum Reprod Update. 2017;23(6):681-705.
- Sermondade N, Faure C, Fezeu L, et al. BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis. Hum Reprod Update. 2013;19(3):221-31.
- Eriksson J, Haring R, Grarup N, et al. Causal relationship between obesity and serum testosterone status in men: a bi-directional Mendelian randomization analysis. PLoS ONE. 2017;12(4):e0176277.
- Davidson LM, Millar K, Jones C, Fatum M, Coward K. Deleterious effects of obesity upon the hormonal and molecular mechanisms controlling spermatogenesis and male fertility. Hum Fertil (Camb). 2015;18(3):184-93.
- Cavayero CT, Cooper MA, Harlin SL. Adult-acquired hidden penis in obese patients: a critical survey of the literature. J Am Osteopath Assoc. 2015;115(3):150-6.
Video production by Glass Entertainment
Motion graphics by Avocado Video
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
In the ABCs of health consequences of obesity, if A is for Arthritis, and B is for Back Pain and Blood Pressure, C is for Cancer, and D is Diabetes, then E is for Encephalopathy.
Encephalopathy means brain disease. There’s consistent data linking obesity in middle age to higher risk of dementia later in life. Overweight individuals have about a third higher risk, and those who are obese in mid-life seem to have about 90 percent greater risk of becoming demented. The risk isn’t just limited to future dysfunction, though. People with excess body weight don’t appear to think as clearly at any age.
Obese individuals show broad impairments in what are called executive functions of the brain, such as working memory, decision-making, planning, cognitive flexibility, and verbal fluency. These “play a critical role in everyday life.”
People may think about their obesity and the resulting stigma they experience as much as five times an hour, but the cognitive deficits do not appear to arise just from distraction; there are structural brain differences between normal weight and overweight individuals.
A review entitled “Does the brain shrink as the waist expands?” noted gray matter atrophy across all ages among those carrying excess body fat. This reduced brain volume has then been correlated with the lower executive function. Compromised integrity of the rest of the brain—the white matter—suggests accelerated brain aging, even in young adults and children with obesity. Cognitive deficits in young populations suggest it’s something about the obesity itself that’s affecting brain function, rather than a later clinical consequence, such as high blood pressure. Purported mechanisms for this executive dysfunction include obesity-related inflammation and oxidative stress.
So, does weight loss improve cognitive function? Based on a meta-analysis of 20 studies, mental performance across a variety of domains can be significantly improved with even modest weight loss; though no studies have yet to be done to determine if this then translates into a normalization of Alzheimer’s disease risk.
F is for Fertility, or rather failed fertility. Overweight couples struggling to have children “should be educated on the detrimental effects of fatness,” one meta-analysis concluded, as weight loss is associated with an improvement in pregnancy rates among infertile women. Men also may suffer impaired fertility. The heavier a man is, the greater their risk of having a low sperm count or being completely sterile. This may in part be due to the effects of excess body fat on testosterone levels.
Fat isn’t just the primary site of estrogen production in postmenopausal women, but in men as well. There’s an enzyme in body fat that actually converts testosterone into estrogen. Men even going from obese to just overweight could potentially raise testosterone levels in their blood 13 percent.
A more dramatic cause of infertility in obese men is called “hidden penis.” Also referred to in the medical literature as buried penis, concealed penis, or inconspicuous penis, it occurs when excess fat in the pubic area subsumes the male member (since the base is attached internally to the pubic bone). It’s also called trapped penis, because the moist enfolding skin surfaces can result in a chronic inflammatory dermatitis leading to scarring, requiring a surgical intervention. So, “F” may also stand for Free Willy.
Please consider volunteering to help out on the site.
- Pedditzi E, Peters R, Beckett N. The risk of overweight/obesity in mid-life and late life for the development of dementia: a systematic review and meta-analysis of longitudinal studies. Age Ageing. 2016;45(1):14-21.
- Loef M, Walach H. Midlife obesity and dementia: meta-analysis and adjusted forecast of dementia prevalence in the United States and China. Obesity (Silver Spring). 2013;21(1):E51-5.
- Yang Y, Shields GS, Guo C, Liu Y. Executive function performance in obesity and overweight individuals: a meta-analysis and review. Neurosci Biobehav Rev. 2018;84:225-44.
- McCrady-Spitzer SK, Levine JA. Nonexercise activity thermogenesis: a way forward to treat the worldwide obesity epidemic. Surg Obes Relat Dis. 2012;8(5):501-6.
- Willette AA, Kapogiannis D. Does the brain shrink as the waist expands? Ageing Res Rev. 2015;20:86-97.
- Walther K, Birdsill AC, Glisky EL, Ryan L. Structural brain differences and cognitive functioning related to body mass index in older females. Hum Brain Mapp. 2010;31(7):1052-64.
- Kullmann S, Schweizer F, Veit R, Fritsche A, Preissl H. Compromised white matter integrity in obesity. Obes Rev. 2015;16(4):273-81.
- Veronese N, Facchini S, Stubbs B, et al. Weight loss is associated with improvements in cognitive function among overweight and obese people: a systematic review and meta-analysis. Neurosci Biobehav Rev. 2017;72:87-94.
- Best D, Avenell A, Bhattacharya S. How effective are weight-loss interventions for improving fertility in women and men who are overweight or obese? A systematic review and meta-analysis of the evidence. Hum Reprod Update. 2017;23(6):681-705.
- Sermondade N, Faure C, Fezeu L, et al. BMI in relation to sperm count: an updated systematic review and collaborative meta-analysis. Hum Reprod Update. 2013;19(3):221-31.
- Eriksson J, Haring R, Grarup N, et al. Causal relationship between obesity and serum testosterone status in men: a bi-directional Mendelian randomization analysis. PLoS ONE. 2017;12(4):e0176277.
- Davidson LM, Millar K, Jones C, Fatum M, Coward K. Deleterious effects of obesity upon the hormonal and molecular mechanisms controlling spermatogenesis and male fertility. Hum Fertil (Camb). 2015;18(3):184-93.
- Cavayero CT, Cooper MA, Harlin SL. Adult-acquired hidden penis in obese patients: a critical survey of the literature. J Am Osteopath Assoc. 2015;115(3):150-6.
Video production by Glass Entertainment
Motion graphics by Avocado Video
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Title
The Effects of Obesity on Dementia, Brain Function, and Fertility
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
If you missed the previous videos, see The Best Knee Replacement Alternative for Osteoarthritis Treatment and The Effects of Obesity on Back Pain, Blood Pressure, Cancer, and Diabetes.
I continue the topic of obesity and weight with these videos:
- The Effects of Obesity on Gallstones, Acid Reflux, and Cardiovascular Disease
- The Effects of Obesity on the Immune System and Kidney and Liver Disease
- What’s the Ideal BMI?
- What’s the Ideal Waist Size?
I cover all of this and more at length in my book How Not to Diet. And, its companion—the brand-new How Not to Diet Cookbook—has more than 100 delicious, weight-conscious recipes.
For more on the health conditions discussed in this video, see the Alzheimer’s disease, cognition, and fertility topic pages.
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