- Click here for explanation of classification scheme.

1. To compare the RMR and thermogenic effect of food in a group of vegetarians compared to a group of subjects on a Mediterranean diet.
2. To investigate if a vegetarian diet can influence energy metabolism and induce lower body weight.

Definitions

• Steady state: 20 min, nonstop period when consecutive differences in measurements were <5%.

1. Understand and give written consent
2. For vegetarian group: vegetarian for at least 1 year; For omnivores university population in clinical nutrition department (physicians, dietitians, medical students following a Mediterranean diet rich in CHO and low in fats:
3. Healthy.

1. Refusal to consent
2. Not meeting inclusion criteria for vegetarianism
3. Unhealthy.

ANTHROPOMETRIC

• Ht measured? Yes
• Wt measured? Yes
• Fat-free mass measured? No

CLINICAL

• Monitored heart rate? No
• Body temperature? No
• Medications administered? No

Resting energy expenditure

• IC type: MMC Horizon
• Equipment of Calibration:
• Coefficient of variation using std gases: No
• Rest before measure (state length of time rested if available): ~20
• Measurement length: >35 min
• Measurement duration: 3 hr
• Steady state: Yes
• Fasting length: 12 hr
• Exercise restrictions XX hr prior to test? Not specified
• Room temp: Not specified
• No. of measures within the measurement period: 1
• Were some measures eliminated? Yes, amount to achieve steady state
• Were a set of measurements averaged? Yes, the 15 min period
• IF avg., identify length of each measure & no. of measurements?
• Coefficient of variation in subjects’ measures? No
• Training of measurer? NS
• Subject training of measuring process? Yes

DIETARY

• 3-day food diaries were completed to verify vegetarian status; Dietary records were analyzed for total energy and nutrient content;
• The meal had to be eaten in 10 mins: 100 g pasta w/tomatoes and olive oil (5 g); 30 grams of bread=515 kcal: 80% CHO; 10% prot; 9% fat.

Outcome(s) and other measures

1. Measured REE [(VO₂, l/min), VCO₂ (l/min; ml/kg/min), RQ, ventilation (l/min)].
2. Macronutrient intake (protein, CHO, lipids, fiber and alcohol)
3. Independent variables of weight, height, age, BMI, and fat-free mass, fat mass

Blinding used: No

• N=32 (12M;20F)

Vegetarians, n=16 (6M;10F)

• (N=5 vegans; 11 lacto-ovo vegetarians)
• Mean age: 34±9 y
• BMI 21±2

Omnivores (Mediterranean diet), n=16 (6M;10F)

• Mean age: 30±5 y
• BMI 22±3

Statistical tests

Comparisons between 2 groups by ANOVA; Man values for RQ, RMR and TEF, adjusting for weight, age and gender by multiple regression

ANTHROPOMETRIC

	Vegetarians Mean±SD	Omnivores Mean±SD
kJ/day	7727±3516	8970±2273
kcal/day	1847±840	2144±543
Protein, %	10.1±1.7	13.4±2.5a
Protein, g/day	44.9±18.3	70.1±14.9 a
Animal protein, g/day	13.2±13.1	40.2±12.9 a
Vegetable protein, g/day a	33.1±11.3	27.2±7.7
Carbohydrates, %	62.0±10.2	56.2±5.8
Lipids, %	28.6±9.7	28.4±5.4
Fiber, g/d	30.5±16.7	16.5±7.9 b
Alcohol, g/day	0.5±1.5	8.9±12.2 b

^a P<0.001; ^b P<0.05

The percent of protein intake was significantly higher in omnivorous subjects while fiber /day was significantly higher in vegetarian group. The % of energy from CHO was almost significantly higher in vegetarians than omnivores.

INDIRECT CALORIMETRY RESULTS

	Vegetarians Mean±SD	Omnivores Mean±SD
RQ	0.84±0.09	0.88±0.13
RMR, kJ/min	4.23±0.96	4.06±0.54
RMR, kcal/min	1.01±0.23	0.97±0.13
TEF, ?kJ/min	0.50±0.25	0.38±0.25
TEF, ?kcal/min	0.12±0.06	0.09±0.06
TEF, % energy	12.0±7.2	10±6.8
RQ b	0.85±0.1	0.88±0.1
RMR, kJ/min b	4.27±0.63	4.02±0.38
RMR, kcal/min b	1.02±0.15	0.96±0.09
TEF, ?kJ/min b	0.50±0.29	0.38±0.25
TEF, ?kcal/min b	0.12±0.7	0.09±0.06
TEF, % energy b	12±7	10±6.4

^b After adjustment for weight, age and gender.

No significant differences between groups were observed in RQ, RMR and thermic effect of food. No significant differences were observed in RQs after the meals at the 1^st, 2^nd and 3^rd hour. Results did not change after correcting for weight, age, and gender.

• “Our study failed to show any significant differences in calorimetric measures between vegetarian subjects and omnivorous subjects on a Mediterranean diet. All that was observed was a nonsignificant lower RQ, higher RMR and TEF in vegetarians.”
• “Previous findings suggest differences...Poehlman found a lower TEF in vegetarians; Oberlin et al did not find significant differences in RMR in young vegetarian and non-vegetarian women and Toth and Poehlman showed that RMR in vegetarians was 11% higher than nonvegetarians. The difference disappeared when the high-carbohydrate, low fat diet and high plasma noradrenaline levels of vegetarians were taken into account.”
• “One limitation of our study is the diet of omnivorous subjects was very similar to that of vegetarians, differing only for higher protein and lower fiber content; CHO content was not significantly different.

Other:

• Strengths

“Used appropriate tools to measure diet intake and measure RMR.”

Generalizability/Weaknesses

• “Generalizability to healthy, non-obese adults, both vegetarian and those who adhere to a healthy diet that includes meat”
• “Study biases include sampling methods since the subjects in the Mediterranean diet (i.e., omnivores) were educated in nutrition and healthy eating (e.g., 16.5 grams of fiber/d, 28.4% kcal from fat) and do not represent a “typical” adult in U.S. (e.g., % calories of fat >30 and 0-5 grams fiber/day)/.
• Both groups became more aware of eating patterns since had to keep 3-day food diary
• An intervening variable not measured fat-free mass not measured and thus not analyzed as a covariate; there is no description of how height was measured (if it was) and measuring weight technique (with light clothing or standard clothing; with or without shoes?);
• These are important variables on REE measurement accuracy: possible exercise the day before measure, machine calibration