Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings from the BBC “diet trials”
BMJ 2006; 332 doi: https://doi.org/10.1136/bmj.38833.411204.80 (Published 01 June 2006) Cite this as: BMJ 2006;332:1309All rapid responses
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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
Competing interests: No competing interests
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
Competing interests: No competing interests
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
Senior Science Editor
Advanced Research Press, Inc.
Associate Editor
Nutrition & Metabolism
www.nutritionandmetabolism.com
Reference
1. Goyal SB, Goyal RS. Ren Fail. 1998 Jul;20(4):645-7.
Competing interests:
None declared
Competing interests: No competing interests
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
Competing interests: No competing interests
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
Competing interests: No competing interests
No surprises
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
Competing interests: No competing interests