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BBC “Diet Trials” in the UK: Benefits and Risks?
- Hanh K Huynh, Zhenguo Qiu (30 May 2006)
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Response to A/Prof Huynh
- Helen D Truby (2 June 2006)
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Weight loss diet and renal function
- Anssi H Manninen (2 June 2006)
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Obesogenic environments
- John C Oldroyd (4 June 2006)
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BBC Diet Trials
- Nadim Y Haboubi, Sian Jones (6 June 2006)
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No surprises
- Abdul Zubairu (7 June 2006)
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Hanh K Huynh, Foundations of Medicine Director - Assistant Professor Northern Medical Program University of Northern British Columbia Canada V2N 4Z9, Zhenguo Qiu
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EDITOR-In their attempts to evaluate the most effective “diet program” for weight loss in overweight and obese individuals, Truly et al.(1) compared the four commercial weight loss diets available to adults in the United Kingdom for a six month period, multicentered, randomized and unblinded trial. By the end of the study, all four commercial diets were equally effective in producing similar weight loss results. The amount of fat loss in all 4 groups was significantly greater than in the control group. All 4 diet programs resulted in a reduction in waist circumference. Interestingly, the monthly weight loss was initially high (from 3.8% to 5.5% in 0-2 months with different diet programs) and then slowed down as time progresses (1.3% to 2.7% in 2-6 months with different diet programs). Furthermore, weight rebound was noted after the initial six months, especially for the participants in the unsupported programs. These observations have been commonly reported in other studies: “Losing weight over the short term, and then experiencing a rebound gain in weight” represent the usual experiences for the majority of obese individuals(2). These findings support the recent descriptions by Tremblay and Doucet(3) of several adaptations that would make the maintenance of body weight stability in a reduced obese state more difficult. One of these adaptations is the greater decrease in energy expenditure than previously predicted (either in the resting state or during exercise) and this change is potentially related to the changes in insulin level in the body: subjects with largest increase in postprandial insulinemia following excess energy intake protocol exhibited a significantly greater increase in energy expenditure compared to those whose insulinemia remained stable. In their following up study, Tremblay et al. also demonstrated the greater the decrease in insulinemia, the greater the decrease in resting energy expenditure(4). Consequently, the findings by Truly et al.(1) and other investigators (2 & 4) mentioned in this letter reinforce the importance of adhering to a healthy diet and regular physical activity habits in order to achieve weight loss and maintain body weight stability after the initial weight reduction, and without the detrimental effects of hyperinsulinemia on metabolic health. Researchers at Mayo Clinic recently recommended 6 strategies for sustainable success in weight loss attempt: 1) Make a commitment; 2) Get emotional support; 3) Set a realistic goal; 4) Enjoy healthier foods; 5) Get active and Stay active; 6) Change your lifestyle (5). The statistical analysis was carefully conducted in this study. The data were analyzed from all participants and there was no centre- variation. Homogeneity of variance was also assessed so that the subject- specific effects (which may attribute the difference between groups) could be eliminated. However, as the weight loss was repeatedly measured over time, the serial correlation within subject must be taken into consideration in the analysis. Did the authors consider the intra- correlation in their analysis? 1. Truly H. et al. Randomized controlled trial of four commercial weight loss programmes in the UK: initial findings from the BB “diet trials”. BMJ 2006 May 23 Online First. 2. Froberg K., Andersen L.B. Physical activity and physical fitness in relation to cardiovascular disease in children. http://www.sdu.dk/health/iob/engelsk/Nordplus%20kursus%20SO5/Froberg- Andersen%20EU-review.pdf (accessed 24 May 2006). 3. Tremblay A., Doucet E. Obesity: a disease or a biological adaptation? Obes Rev 2000; 1: 27-35. 4. Tremblay A., Boule N., Doucet E., Woods S.C. Is the insulin resistance syndrome the price to be paid to achieve body weight stability? Int. J. Obesity 2005; 29: 1295-1298. 5. MayoClinic. Weight loss: 6 strategies for success. http://www.mayoclinic.com/health/weight-loss/HQ01625 (accessed 24 May 2006). Competing interests: None declared |
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Helen D Truby, Senior Lecturer Univeristy of Surrey
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The study reported in this weeks BMJ (Truby et al) was designed to test the relative efficacy of 4 different dietary programmes against a delayed treatment control group. The study subjects were free living and no attempt was made to standardise energy intake between the diet groups. This study design combined with a multi-centre randomised design allowed the aims of the study to be achieved with no measurable differences between the groups at baseline suggesting that the diet group allocation was indeed random and there was no clustering effect. The results have been presented as a per protocol approach with the range of weight loss achieved by individuals demonstrated to be extremely variable, with some subjects achieving upto a 24kg weight loss and a few managing to gain weight during the 6 month intervention period. At the end of the 6 month intervention, subjects were free to carry on with the diet to which they had been allocated or not. Relatively few chose to carry on with their allocated diet and those who remained on more supported group based programmes tended to have less weight re-gain. However, subjects who remained on the unsupported programmes also achieved around 10% body weight loss at 12 months. This must also be recognised as success for those individuals. Our study, tries to provide information to practitioners as to how much body weight subjects can expect to lose with a commercial approach and we tried not to intervene with their dieting practices. It is inevitable that subjects weigh and measure themselves on a more regular basis at home than the monthly weigh-ins conducted during this study, therefore we do not report the intra-correlation of weight change over time as it is likely as those dissatisfied with their weight loss (or gain) withdraw from studies and do not provide further information. We agree with A/Prof Huynh that the importance of adhering to a healthy diet with regular physical activity in order to achieve body weight stability after weight loss should be the goal - but we have a long way to go with achieving this outcome. Competing interests: None declared |
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Anssi H Manninen, Senior Science Editor Advanced Research Press, Inc.
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I would like to compliment Truby et al. on their study comparing the effectiveness of four commercial weight loss diets. However, it appears that the authors monitored renal function only in the Atkins group, suggesting that they had a negative bias againts the Atkins diet. Not surprisingly, urea, electrolytes and cystatin C remained within the reference ranges. Obviously, renal function should be monitored in the high-carbohydrate diet groups too. For example, Goyal & Goyal described a case of a young obese man who developed diabetic ketoacidosis after he had been on Ultra Slim Fast as the only source of nutrition for two weeks prior to presentation (1). Their patient subsequently developed acute renal failure from rhabdomyolysis. The authors rightly suggested that "these [high-carbohydrate] supplements should never be taken as the sole source of nutrition especially in obese persons who have underlying insulin resistance". Anssi H. Manninen
Reference 1. Goyal SB, Goyal RS. Ren Fail. 1998 Jul;20(4):645-7. Competing interests: None declared |
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John C Oldroyd, Lecturer in Public Health Deakin University, 221 Burwood Highway, Burwood, Victoria, Australia, 3125
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To the Editor The article by Truby et al [1] is a valuable contribution to the evidence about effective commercial dietary interventions for obesity in overweight and obese individuals. What is a little disappointing is the publication of yet another study on dietary interventions for high risk individuals. Although studies that tell us about dietary effectiveness are important, of far greater public health value are investigations of the social, policy and cultural determinants of obesity. Surely it is time to study public health interventions investigating such things as transport policies to promote physical activity, pricing policies to reduce food insecurity or nutrition interventions in whole communities which aim to improve dietary quality. Until the environments in which we live are made less obesogenic, diets for individuals will have little impact on the obesity epidemic. 1. Truby H, Baic S, deLooy A, Fox K R, Livingstone M B, Logan C M, Macdonald I A, Morgan L M, Taylor M A, Millward D J. Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings from the BBC "diet trials". BMJ, 332(7553): 1309-14, 2006. Competing interests: None declared |
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Nadim Y Haboubi, Consultant Physician Nevill Hall Hospital, Brecon Road. Abergavenny, Np7 7EG, Sian Jones
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BBC DIET TRIALS Truby et al compared the effectiveness of four different weight loss programmes. The principle objectives of weight management are, firstly, to introduce a negative energy balance to reduce body weight. Secondly, to maintain a lower body weight over a longer period over the longer-term. Thirdly, to ensure that people who are obese are following a healthy balanced diet that is low in saturated fats and high in complex carbohydrates. Undoubtedly the low carbohydrate diet is quite popular currently as it achieves a short-term weight loss mainly through reducing appetite. It has been recently shown that the low carbohydrate with high protein and low fat diets might produce even greater weight loss than those who are on conventional low fat diet particularly so for the first six months. However, this did not show any significant difference a year later. The initial rapid weight loss that can be produced by a low carbohydrate diet is not the real loss of body fat but of body water. This happened because of the unbalanced metabolism of fat (ketosis). Though blood lipid and insulin resistant level might improve short-term , mineral loss such bone calcium are increased. It is highly likely that the long-term impact of maintaining such a diet might well increase the risk of cardio-vascular disease. The results of the BBC diet trials also showed that cholesterol level was lower when subjects were on the Atkins diet. However, one would expect that HDL would be higher in the groups who have increased their physical activity, which is naturally more cardio protective. The long term cardiovascular risk of the Atkins diet has been highlighted by the American Heart Association and the British Dietetic Association. The possible ill effect of high protein intake on renal and liver function, might increase the risk of developing renal calculi or liver abnormalities. This is particularly important in morbidly obese subjects who have fatty liver or a decline in their kidney function. It is important to note that those who are on the Atkins diets do restrict their intake from protective foods (such as fruits and wholegrain cereals). This is of concern as research has shown a clear association between poor fruit/ vegetable intake and bowel cancer. There was a clear evidence that the sustainability among the four groups was better in the Rosemary Conley and Weight Watchers group than the others in the trial. In our opinion emphasis on healthy diet, change of lifestyle and increased physical activity is the best solution in obesity management. Dr Haboubi, MD FRCP, Consultant Physician with Special Interest in Obesity Management Ms S Jones, BSc SRD (Hons) Senior Dietician with Special Interest in Obesity Management Competing interests: None declared References 1. Truby H, Baic S, deLooy A, et al. Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings from the BBC “diet trials”. BMJ, 2006: 332, 1309-1311 (3 June) Competing interests: None declared |
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Abdul Zubairu, F1/ House Officer Whiston Hospital, St Helens. L35 5DR
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The results of the Truby et al. randomised controlled trial comparing four commercial weight loss programmes comes as no surprise to myself.(1) Weight control is an energy balance equation and obesity results from an energy intake exceeding energy expenditure. Conversely to lose weight, energy intake must be less than energy expenditure. The Atkins diet (low-carbohydrate) remains controversial. Some experts believe followers are at risk from vitamin and mineral imbalances along with cardiac, liver and renal abnormalities. In a systematic review carried out in the Lancet, low-carbohydrate diets were not endorsed due to the fact that although they may promote weight loss in the short term, the long term effects are still unknown.(2) All four diets used in this trial, indeed any diet, work by restricting food and limiting calories leading to weight loss. These comercial diets may have detrimental effects in the long term. The best advice is to eat a varied diet with the appropriate number of calories combined with physical activity to lose weight. (1)Truby H, Baic S, deLooy A, Fox KR, Livingstone MBE, Logan CM, Macdonald IA, Morgan LM, Taylor MA, Millward DJ. Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings fron the BBC "diet trials" BMJ 2006; 322:1309-11 (2)Astrup A, Larsen TM, Harper A. Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss? Lancet 2004; 364:897-99 Competing interests: None declared |
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