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.
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.
Rapid Response:
BBC “Diet Trials” in the UK: Benefits and Risks?
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