- Click here for explanation of classification scheme.

To determine whether a low calorie wt loss diet containing oats would produce greater improvements in blood pressure (b/p) and lipid profile than a low cal wt loss diet without oats.

This study also measured energy regulation and influence of age.

Wt range limited to BMI of 20-35 kg/m2

Ages 18-75

Men and women

Healthy

Wt stable

Taking meds known to influence body wt or b/p

Significant hx of eating d/o

Strenuous exercise of = 1h/d

Subjects were recruited.

Neither method of recruitment nor source of subjects were reported.

An 8-week study that took place at the Metabolic Research Unit (MRU) of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University.

First 2 weeks (Phase I) all subjects consumed the same diet of usual food items and the level of calories needed to maintain body wt.

In the 6 week wt loss phase (Phase II) subjects were provided a diet of maintenance energy minus 4.2 MJ/d.

For Phase II subjects were randomized to the control or oat diet on the basis of age and gender to ensure similar characteristics in the 2 Phase II groups.  The younger subjects were further randomized by BMI<25 or =25.

Method of randomization not reported.

The oat-free control diet in Phase II was simply a continuation of the Phase I diet.

The experimental diet contained 45g dry wt/4.2MJ of oats.  A daily multivit w/no minerals was given during Phase II to all subjects due to the inadequate vit content of the low cal diet.

Subjects slept at the MRU on the night before a test only.

Subjects ate 3 meals and 1 snack/d.  The oat diet contained oats in all meals and snacks.

Diets were matched for insoluble fiber, pro, cho, and fat.  Na+ and K+ were held constant at each subject’s level of intake in Phase I.

Subjects were required to eat at least 4 meals/week at the MRU.

 

 

No blinding used.

During Phase I and II the following measures were done:

*Body wt, body comp, energy expenditure, b/p, blood tests for metabolic variables, 24-h urine.

Body wt and composition

Wt measured with digital electric scale to 0.01 kg.

Ht measured with fixed-wall stadiometer.

Body comp measured with hydrodensitometry after an overnight fast. Done twice during Phase I and twice in Phase II.

Fat free mass calculated using equations of Siri 1961.

Blood Pressure

Taken at each outpatient visit and each stay at MRU after sitting quietly.

Average systolic and diastolic b/p was determined for wk 2 and subtracted from the avg from wk 8 to determine the effect of the Phase II diet on b/p.

Metabolic parameters

Blood was collected twice in Phase I and once in Phase II.

Plasma glc was measured after overnight fast twice during I and once during II.

Oral glc tolerance once in I and II.

Plasma lipids and lipoproteins once in I and II.

Urinary Na+ and K+ were analyzed.  3 consecutive 24-h urine samples collected in wk 5, and repeated in wk 7 or 8.

 

43 healthy men and women.

*20 men

*23 women

*ages 19-78

control n=21

oat n=22

100% completion rate

 

There were no significant differences in the 2 diet groups in age, wt, BMI, %body fat at baseline.

During Phase II both groups had similar wt changes, indicating diet adherence was good. No sig diff between groups in %wt change compared to initial wt.  No sig diff in change in fat mass (Table 1).

There were no effects of initial BMI, initial %body fat, age or gender on wt loss.  No sig diet x age or diet x gender interactions on wt loss (no data).

At baseline mean b/p was normal in both groups.

Diastolic b/p decreased sig within and between both groups after Phase II (Table 1).

Systolic b/p sig decreased only in the oat group after Phase II (Table 1).

Diet appeared to have an effect on SBP independent of wt loss  When controlling for initial b/p, initial BMI, and wt lost, there was a sig diff found in the effect of the oat diet on decreasing SBP (P=0.026) but not DBP (P=0.8).

 

Table 1.  Between and within group differences after treatment.

	Control	Oats	Between groups	Within group
Absolute wt change	-4.0 ± 1.1 kg	-3.9 ± 1.6 kg	P=0.8	0
Wt change as % of initial wt	-5.3 ± 1.6%	-5.5 ± 2.8%	P=0.76	0
Fat mass change	-2.7 ± 1.6 kg	-2.5 ± 1.3 kg	P=0.65	0
Change SBP	-1 ± 10 mmHg	-6 ± 7 mmHg	0	P=0.7/P=0.0001
Change DBP	-3 ± 5 mmHg	-4 ± 6 mmHg	P=0.4	P=0.013/P=0.007
Urinary Na+ excretion	2498 ± 732 mg/d	2769 ± 814 mg/d	X	0
Changes in TG mmol/L	-0.22 ± 0.23	-0.36 ± 0.36	X	0
Change in TC mmo/L	-3.4 ± 0.5	-0.87 ± 0.47	P=0.003	0
Changes in VLDL mmol/L	-0.1± 0.1	-0.16 ± 0.17	X	0
Changes in LDL mmol/L	-0.2 ± 0.41	-0.6 ± 0.41	P=0.008	0
Changes in HDL mmol/L	-0.04 ± 0.14	0.09 ± 0.13	X	0

X = no significant difference. P value not reported

Adding oats to a wt loss diet may have the benefit of reducing SBP. Sustaining a reduction of SBP to the degree seen in this study (6 mm HG) would have a considerable effect on preventing CVD.

The subjects in this study were normotensive however a low cal wt loss diet that includes oats may have an even greater effect on hypertensive subjects.

The same may be said for subjects with mild to moderate dyslipidemia.

It is unclear if there would continue to be improvement in lipid profiles or b/p after wt stabilization.

The addition of oats to an unhealthy wt loss diet to improve lipids or b/p  is not recommended.

In this study oats were easy to incorporate, was accepted by the subjects and caused no GI complaints.

 

Government:	NIH,US Dept. of Agriculture,
Industry:	Quaker Oates Company Food Company:

Small sample size.

No report of how subjects were recruited or from where.

No report on method of randomization.

Control and experimental groups were equal in all characteristics.

Sample included both sexes and huge age span so it shows promise for generalizability if the sample size was larger.