Sunday, March 8, 2009

The Studies

Obesity in middle age and future risk of dementia
Rachel A Whitmer, Erica P Gunderson, Elizabeth Barrett-Connor, et al. : a 27 year longitudinal population based study. BMJ 2005;330:1360

To evaluate any association between obesity in middle age, measured by body mass index and skinfold thickness, and risk of dementia later in life.

Analysis of prospective data from a multiethnic population based cohort.

Kaiser Permanente Northern California Medical Group, a healthcare delivery organisation.

10 276 men and women who underwent detailed health evaluations from 1964 to 1973 when they were aged 40-45 and who were still members of the health plan in 1994.

Main outcome measures
Diagnosis of dementia from January 1994 to April 2003. Time to diagnosis was analysed with Cox proportional hazard models adjusted for age, sex, race, education, smoking, alcohol use, marital status, diabetes, hypertension, hyperlipidaemia, stroke, and ischaemic heart disease.

Dementia was diagnosed in 713 (6.9%) participants. Obese people (body mass index >30) had a 74% increased risk of dementia (hazard ratio 1.74, 95% confidence interval 1.34 to 2.26), while overweight people (body mass index 25.0-29.9) had a 35% greater risk of dementia (1.35, 1.14 to 1.60) compared with those of normal weight (body mass index 18.6-24.9). Compared with those in the lowest fifth, men and women in the highest fifth of the distribution of subscapular or tricep skinfold thickness had a 72% and 59% greater risk of dementia, respectively (1.72, 1.36 to 2.18, and 1.59, 1.24 to 2.04).

Obesity in middle age increases the risk of future dementia independently of comorbid conditions

Increasing fat intake reduces deaths in Swedish study

Leosdottir M, Nilsson PM, Nilsson J-A, Mansson H, Berglund G (Lund University, Malmo, Sweden). Dietary fat intake and early mortality patterns — data from The Malmo Diet and Cancer Study. J Intern Med 2005; 258: 153-165.

Objectives. Most current dietary guidelines encourage limiting relative fat intake to <30%>

The Malmo Diet and Cancer Study was set in the city of Malmo, southern Sweden. A total of 28 098 middle-aged individuals participated in the study 1991-1996.

Main outcome measures. Subjects were categorized by quartiles of relative fat intake, with the first quartile used as a reference point in estimating multivariate relative risks (RR; 95% CI, Cox's regression model). Adjustments were made for confounding by age and various lifestyle factors.Results.

Women in the fourth quartile of total fat intake had a significantly higher RR of cancer mortality (RR 1.46; CI 1.04-2.04).[but see below] A significant downwards trend was observed for cardiovascular mortality amongst men from the first to the fourth quartile (P = 0.028). No deteriorating effects of high saturated fat intake were observed for either sex for any cause of death. Beneficial effects of a relatively high intake of unsaturated fats were not uniform.

With the exception of cancer mortality for women, individuals receiving more than 30% of their total daily energy from fat and more than 10% from saturated fat, did not have increased mortality. Current dietary guidelines concerning fat intake are thus generally not supported by our observational results.

COMMENT: In this study, deaths from heart disease, cancer and total deaths in both sexes went down as fat intake rose. This was particularly noticeable with saturated fats.The one glitch was that cancers increased in women (not men) with the highest intake of fat — but significantly, this was confined entirely to intakes of monounsaturated fats (from 'healthy' oils such as olive oil and flaxseed oil).Strangely, monounsaturated fats had the opposite effect in men by reducing the overall death rate.The effects on heart disease are also interesting: In men, increasing total fat and saturated fat reduced their death rates; in women increasing or reducing fats didn't make any difference.

The researchers write:
"With the exception of cancer mortality for women in the highest quartile of relative fat intake, individuals receiving more than 30% of their total daily energy from fat did not have increased mortality. Men in the fourth quartile of total fat intake, receiving almost 50% of their total energy intake from fat, had the lowest cardiovascular mortality. Receiving more than 10% of total energy intake from saturated fat did not have a significant effect on all-cause, cardiovascular or cancer mortality for men or women.

Beneficial effects of relatively high intakes of unsaturated fats were not uniform, and having a high index of unsaturated fat compared with saturated fat intake did not have any detectable effect on mortality.""With our results added to the pool of evidence from large-scale prospective cohort studies on dietary fat, disease and mortality, traditional dietary guidelines concerning fat intake are thus generally not strongly supported."
Barry Groves, Second Opinions UK

How Low-Carb Diets Help Overweight Diabetic Persons

Jørgen Vesti Nielsen, Eva Jönsson, Anna-Karin Nilsson. Lasting Improvement of Hyperglycaemia and Bodyweight: Low-carbohydrate Diet in Type 2 Diabetes. ? A Brief Report. Upsala J Med Sci 109: 179?184, 2005Dept of Medicine, Blekingesjukhuset, Karlshamn, Sweden

In two groups of obese patients with type 2 diabetes the effects of 2 different diet compositions were tested with regard to glycaemic control and bodyweight.

A group of 16 obese patients with type 2 diabetes was advised on a low-carbohydrate diet, 1800 kcal for men and 1600 kcal for women, distributed as 20 % carbohydrates, 30 % protein and 50 % fat. Fifteen obese diabetes patients on a high-carbohydrate diet were control group.

Their diet, 1600-1800 kcal for men and 1400-1600 kcal for women, consisted of approximately 60 % carbohydrates, 15 % protein and 25 % fat.Positive effects on the glucose levels were seen very soon. After 6 months a marked reduction in bodyweight of patients in the low-carbohydrate diet group was observed, and this remained one year later.

After 6 months the mean changes in the low-carbohydrate group and the control group respectively were (±SD):
fasting blood glucose (f-BG): -3.4 ± 2.9 and -0.6 ± 2.9 mmol/l;
HBA1c: -1.4 ± 1.1 % and -0.6 ± 1.4 %;
Body Weight: -11.4 ± 4 kg and -1.8 ± 3.8 kg;
BMI: -4.1 ± 1.3 kg/m2 and -0.7 ± 1.3 kg/m2. Large changes in blood glucose levels were seen immediately.

A low-carbohydrate diet is an effective tool in the treatment of obese patients with type 2 diabetes. A free full-text copy of this article can be found at the web page of Upsala J Med Sci:

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