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Biomedical subjects

P M Warwick

Publications and source records attributed to P M Warwick.

15 recordsLinked to original sources
PubMed1996

Energy expenditure in free-living smokers and nonsmokers: comparison between factorial, intake-balance, and doubly labeled water measures.

Free-living energy expenditure (EE) was measured in 11 smokers (6 females, 5 males) and 10 nonsmokers (6 females, 4 males) by using three methods. Factorial measures (FEE) used measured basal metabolic rate (BMR), records of time spent in six activity categories over 28 d, and average published energy costs of activities. Intake-balance measures (IBEE) used recorded dietary energy intake and changes in energy stores over 28 d. Doubly labeled water measures (DLWEE) used a two-point method over 8-12 d. Level of activity (1.54 +/- 0.07 and 1.55 +/- 0.06 x BMR) and FEE (9573 +/- 1501 and 9540 +/- 1663 kJ/d) were not different between smokers and nonsmokers, respectively. DLWEE was higher than FEE in both smokers (25.9 +/- 13.5%, P < 0.001) and nonsmokers (10.4 +/- 13.8%, P < 0.05), suggesting factorial underestimation in both groups, although the difference between DLWEE and FEE was significantly greater in smokers than in nonsmokers (P < 0.02). IBEE was higher than FEE in smokers (7.5 +/- 10.1%, P < 0.05) but not different from FEE in nonsmokers (2.7 +/- 16.6%), suggesting factorial underestimation in smokers only. DLWEE was higher than IBEE in smokers (13.8 +/- 12.6%, P < 0.01) but not significantly different from IBEE in nonsmokers (6.2 +/- 16.0%). The discrepancies between DLWEE and IBEE in smokers and DLWEE and FEE in nonsmokers preclude conclusion about absolute levels of daily EE. However, both DLWEE-FEE and IBEE-FEE comparisons suggest that our factorial method underestimates free-living EE in smokers relative to nonsmokers, although the effect is larger with the DLWEE-FEE than with the IBEE-FEE comparison.

Adult↗
PubMed1995

No evidence for a chronic effect of smoking on energy expenditure.

OBJECTIVE: To investigate whether effects of smoking on energy expenditure (EE) extend chronically beyond smoking the last cigarette. DESIGN: Eight subjects (5M,3F) were studied over three consecutive months, after smoking as normal (S) on 1-3 occasions, and after not smoking for 4-8 weeks (NS) on 1-2 occasions. On each occasion subjects underwent one 32-h measurement of EE in a respiration chamber (8-h overnight plus a 24-h day, with no smoking in the chamber) and one measure of basal metabolic rate (BMR) on exit from the chamber. Statistical differences were determined using paired t-tests. RESULTS: There were no differences between S and NS for any of the EE measures, either including (n = 8) or excluding (n = 5) three subjects whose urinary cotinine excretions suggested failure to stop smoking during NS. For S and NS (N = 5) respectively, overnight EEs during the first night in the respiration chamber were 2.08 +/- 0.38 and 2.10 +/- 0.42 MJ/8-h; 24-h EEs during 12-36 hours after the last cigarette were 8.38 +/- 1.6 and 8.24 +/- 1.34 MJ/day, and BMRs were 6.51 +/- 1.21 and 6.50 +/- 1.07 MJ/day. CONCLUSION: We found no evidence for a chronic effect of smoking on EE.

Adult↗
PubMed1993

Prediction of twenty-four-hour energy expenditure in a respiration chamber in smokers and non-smokers.

Fourteen subjects (seven smokers, seven non-smokers) underwent at least one measurement of 24-h energy expenditure (EE) in a respiration chamber, smoking or not smoking as normal. Activity levels (AL) were calculated as multiples of basal metabolic rate (BMR) from records of time spent in specified activity categories and their average published energy costs. Predicted 24-h EE was estimated by multiplying AL by BMR measured on exit from the chamber. Smokers smoked an average of 18.6 cigarettes during the 24-h EE measurement (range 9-29). Measured 24-h EE was higher than predicted in the smokers (7.1%, P < 0.001) but not significantly different from predicted in the non-smokers (2.6% lower). We conclude that smoking increases 24-h EE and that factorial prediction of EE using average published energy costs of activities under-estimates 24-h EE in smokers but not in non-smokers.

Activities of Daily Living↗
PubMed1990

Influence of mild cold on 24 h energy expenditure in 'normally' clothed adults.

Ten subjects aged 19-35 years (four men and six women) underwent two measurements of 24 h energy expenditure (EE) in a whole-body respiration calorimeter, one at a temperature of 28 degrees and one at 20 degrees. Choice of clothing was allowed. Dietary intake was standardized and subjects were asked to follow the same pattern of activity during both measurements. Mean 24 h EE was significantly greater at the cooler temperature by 5.0 (SD 5.5)%, with individual differences ranging from 4.6% lower to 12.6% higher. The difference in EE at the two temperatures was similar during the day and the night and occurred even though subjects wore more clothes and used more bedding at 20 degrees. No relationship was observed between response to 20 degrees and body-weight status. In conclusion, the assumption that mild cold is unlikely to affect EE in subjects wearing normal clothing may be incorrect.

Adult↗
PubMed1988

Prediction of energy expenditure: simplified FAO/WHO/UNU factorial method vs continuous respirometry and habitual energy intake.

This study assessed a simple factorial method to predict energy expenditure (EE) in confined and free-living subjects. Thirteen subjects (seven male, 6 female) were studied on four occasions each. Measurements included BMR, 24-h EE by continuous respirometry, 4-d records of intake and activities, body weight, and urine collections. Agreement between measured and predicted 24-h EE was within +/- 2% for group results and +/- 10% for most individuals. Individual agreement was improved to within +/- 5% by using measured rather than predicted BMR. Habitual energy intake was 7.3% greater (p less than 0.05) than predicted EE in males and 5.1% less (NS) in females. Validatory data suggested overrecording of intake in males and underrecording in females. Large individual differences between habitual intake and predicted EE were observed but were significantly (p less than 0.01) correlated with both weight change and protein balance. Our simple factorial method provided acceptable estimates of EE in the subjects studied.

Adult↗
PubMed1988

Dietary intake of healthy subjects before and one year after dietary advice.

This study was conducted to follow up healthy subjects from a previous study (Warwick & Williams, 1987) in which favourable dietary changes were achieved during 1 week immediately after dietary advice but were accompanied by reduced energy intakes and weight loss. Twenty-one subjects (8m, 13f; 57 per cent of the original group) participated in the follow-up study. Dietary intakes were measured using 7-d weighed records on three occasions: before, immediately after and 1 year after receiving dietary advice. Intakes 1 year after dietary advice continued to show some of the favourable changes observed immediately after the advice but were not accompanied by reduced energy intakes and weight loss. Intakes before, immediately after, and 1 year after dietary advice respectively were: energy, 9.0, 7.8 and 8.9 MJ/d (2150, 1860 and 2120 kcal/d); fat, 36.9, 32.9 and 31.5 per cent of total energy; carbohydrate, 44.2, 47.9 and 49.6 per cent of total energy; dietary fibre, 32, 36 and 36 g/d; sodium, 116, 97 and 110 mmol/d; and Na:K ratio, 1.4, 1.2 and 1.2 mmol. Nutrient densities for fibre and most micronutrients tended to be higher 1 year after dietary advice than before, but were highest immediately after the advice. Nutrient densities for sodium and total sugars did not vary between the 3 study weeks. It was concluded that our healthy subjects adapted their intakes to maintain energy balance while retaining favourable dietary changes for at least 1 year after dietary advice.

Adult↗
PubMed1987

Dietary intake of individuals interested in eating a healthy diet: a validated study of intake before and after dietary advice.

The food intake of 37 adult volunteers (12 M, 25 F) interested in eating a healthy diet was measured on two occasions by the 7-day weighed record method. In week 1 subjects consumed their habitual diet and in week 2 attempted to follow dietary recommendations (DR). Intakes were compared with recommended dietary allowances (RDA) and with dietary guidelines (DG). Validation of recorded energy intakes against changes in body weight, and sodium, potassium and nitrogen intakes against urine excretions suggested reliable dietary records in both study weeks. Mean dietary intakes in week 1 met the RDA for all nutrients studied except for energy (which was close) and zinc (in females only). Daily energy intake was 2160 kcal (9.04 MJ) in week 1 and 1810 kcal (7.56 MJ) in week 2, and subjects lost weight during week 2. Absolute intakes of vitamins and minerals were similar in both study weeks, thus increasing nutrient density in week 2 and suggesting improved dietary quality. Mean dietary intakes in week 1 conformed more closely to DG than commonly reported and changed in the direction recommended in week 2. Mean daily intakes in week 1 and week 2 respectively were: fibre, 31 and 34 g; sodium 114 and 90 mmol; Na:K ratio, 1.37 and 1.10; alcohol, 3.3 and 2.3 per cent of total energy; fat, 38.7 and 34.2 per cent of food energy or 37.4 and 33.4 per cent of total energy. Intake of fibre increased with respect to energy but sodium intake per unit energy did not decrease. Energy intake was positively related to sodium, fibre and zinc intakes and influenced ease of conformity to DR for these nutrients. It is concluded that our motivated subjects were able to make short-term dietary changes consistent with DR. Whether or not these changes continue in the long term is the subject of a follow-up study.

Adult↗
PubMed1987

The effect of smoking two cigarettes on resting metabolic rate with and without food.

Resting metabolic rate (RMR) was measured using a ventilated hood apparatus in 15 subjects before (BMR) and for 5 h after (5HEE) four treatments. In 10 smokers (five occasional and five habitual) the treatments were: food (600 kcal (2.51 MJ) breakfast) with and without smoking two cigarettes (F +/- S) and no food with and without smoking (NF +/- S). In five non-smokers duplicate measurements of food (F-S) and no food (NF-S) were made. In non-smokers the thermic effect of food (TEF) averaged 9.35 per cent of the ingested energy. Duplicate measures of 5HEE showed good reproducibility both with and without food (c.v. 2.5 and 1.3 per cent respectively). In smokers, RMR did not increase after smoking even during the first 15-30 min. There were no apparent differences in response between occasional and habitual smokers. 5HEE and delta 5HEE (5HEE minus BMR) were significantly lower after food with smoking than without smoking (-16 kcal (67 kJ)/5 h, P less than 0.001 and -14 kcal (59 kJ)/5 h, P less than 0.02 respectively) but not significantly lower after smoking without food. TEF was lower with smoking (8.6 per cent of ingested energy) than without smoking (10.0 per cent of ingested energy) but the difference was not significant (P = 0.23). TEF in smokers regardless of treatment averaged 9.3 per cent of the ingested energy. We conclude that any effects of smoking two cigarettes in isolation after overnight deprivation are too small or too variable to consistently influence RMR or the thermic effect of food.

Adult↗
PubMed1981

The effect of addition of exercise to a regime of dietary restriction on weight loss, nitrogen balance, resting metabolic rate and spontaneous physical activity in three obese women in a metabolic ward.

Three obese women were studied for periods of 12-13 weeks while on a constant reducing diet (800 kcal/day) in a metabolic ward. Body weight and nitrogen balance were measured throughout the study and patients kept continuous diary card records of their physical activity. Fasting resting metabolic (BMR) was measured twice weekly using a ventilated hood apparatus. Each patient acted as her own control by alternatively exercising (2 h/d on a bicycle ergometer) or not exercising for consecutive 3-4 week periods. Rate of weight loss was not increased by this level of exercise over the 3-4 week periods. This surprising result could not be explained by a decreased nitrogen loss since nitrogen balance was not significantly affected by the exercise, not could it be explained by a compensatory decrease in subsequent energy expenditure since BMR and spontaneous activity was not measurably affected by the exercise. However, since exercise increases muscle glycogen stores it may have been this effect which negated the expected increase in weight loss during ther exercise programme.

Adolescent↗
PubMed1980

Predisposition to obesity.

65 women whose build ranged from normal to grossly obese were investigated to test the hypothesis that obese people, especially those with a genetic predisposition to obesity (manifest by early onset and family history of obesity), have a low energy expenditure. For the group as a whole, resting metabolic rate was related to obesity index, but the age of onset and family history of obesity had no effect on this relationship. The findings suggest that a familial predisposition to obesity is more likely to relate to energy intake than to energy expenditure.

Adolescent↗
PubMed1980

Factors influencing the composition of the weight lost by obese patients on a reducing diet.

1. Weight loss, resting metabolic rate and nitrogen loss were measured in forty obese inpatients on reducing diets. 2. Five subjects ate 3.55 MJ/d for 6 weeks (Expt 1). Twenty-one subjects ate 4.2 MJ/d for the first week, 2.0 MJ/d for the second week and 4.2 MJ/d for the third week (Expt 2). Fourteen subjects ate 3.4 MJ/d for the first week and then 0.87 MJ protein or carbohydrate for the second or third weeks, using a cross-over design for alternate patients (Expt 3). 3. Patients in Expt 1 had highest weight loss and N loss in the first 2 weeks, but adapated to the energy restriction over the remaining weeks. On average subjects were in N balance at the end of the study. 4. In Expt 2 patients eating 2.0 MJ/d in week 2 showed increased weight loss compared with week 1. N loss was not raised but it failed to decrease as it had in Expt 1. Weight loss and N loss were reduced on return to 4.2 MJ/d for a third week. 5. In Expt 3 patients eating 0.87 MJ protein showed significantly more weight loss and less N loss than patients eating 0.87 MJ carbohydrate. 6. Resting metabolic rate decreased with time on the low-energy diet, but the manipulations of energy or protein content did not significantly affect the pattern of decrease. 7. Both weight loss and N loss were greater the lower the energy intake, and both decreased with time. Diets with a high protein:energy value give a favourable value for N:weight loss at each level of energy intake.

Adolescent↗
PubMed1978

Factors determining weight loss in obese patients in a metabolic ward.

A metabolic unit is described in which it is possible to make controlled measurements of energy balance in patients with various types and degrees of obesity. Thirty-seven obese women were studied for three consecutive one-week periods on a diet which provided an average of 3.4MJ (800 kcal) daily, and some also undertook an exercise programme involving the expenditure of 850--1275 kJ (200--300 kcal) extra per day. The distribution of energy intake was varied from week to week, and within the day (nibbling and gorging), but neither these variations in dietary pattern nor the exercise programme significantly affected the total weight loss over the three-week study period. Very large variations were observed between individuals. Total weight loss over the three-week study period ranged from 1.6 to 9.8 kg. The best predictor of weight loss in a patient on a strictly controlled diet is the resting metabolic rate. The previous diet also affects weight loss: patients who had been keeping to a reducing diet before admission lost less weight, especially in the first week, than those who had not been dieting immediately before admission to hospital.

Body Height↗