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Weight loss and blood pressure

Systematic review
Results
Comment


Bandolier is always on the look out for good evidence about healthy living, and especially about how to avoid having to take antihypertensive medicines. While it is reasonably clear that being overweight may predispose to higher blood pressure, what is the evidence that losing weight reduces blood pressure? And if so, by how much?


Part of the problem in understanding the evidence is the complexity of it all. Are we talking here about normotensive or hypertensive people? Are they on any medicines already? Is weight loss achieved by calorie restriction, exercise, both, or with some added pharmacological help? And what about the length of time taken to lose the weight?


A new and sensible systematic review [1] goes a long way to helping us understand how losing weight helps reduce blood pressure.


Systematic review


Randomised trials of weight reduction and effects on blood pressure were sought by examining four electronic databases and examination of reference lists from published articles. Those fulfilling inclusion criteria were in English, lasted at least eight weeks, and were of non-pharmacological reduction of body weight.


Where weight and blood pressure were recorded at various points in time during the trial, information was abstracted at the point at which maximal blood pressure reduction was achieved. In the absence of this information, the effect at the end of the study was used.


Results


There were 25 eligible trials with 4,874 subjects in trials lasting between eight and 260 weeks, with an average of 67 weeks. The overall mean initial body weight was 88 kg and the overall mean BMI was 31 kg/sq m. Studies most often included both men and women, and the mean ages in the studies varied between 37 and 66 years. About half the populations had initial blood pressures of more than 140/90 mmHg, and about a quarter of the populations were taking antihypertensive medicines. Overall the study withdrawal rate was 4.8%.


The overall mean weight reduction was 5 kg, about a 6% reduction in body weight from baseline. Slightly greater weight loss was found in calorie restricted (7 kg) than exercise alone (3 kg), and combined calorie restriction plus exercise (6 kg).


Changes in systolic and diastolic blood pressure were generally proportional to the amount of weight lost. The relationship for systolic blood pressure is in Figure 1. Overall both systolic and diastolic blood pressure fell by about 1 mmHg for every 1 kg of weight lost.



Figure 1: Relationship between weight loss and reduction in systolic blood pressure





Various subgroup analyses suggested that this relationship held for younger and older people, for studies with more or fewer women, in people who were hypertensive and normotensive, for weight lost by different methods, whatever the initial BMI, and for smaller and larger weight reductions. There were hints that larger reductions in blood pressure for every kg lost might have been seen in Asian populations and people on antihypertensive medicines, but hints they were.


Comment


What we have here is a common sense review. It used randomised trials of a sensible duration, and found a consistent relationship between weight loss and reductions in systolic and diastolic blood pressure. This is particularly good news for those of a certain age, when weight tends to be a bit on the high side, and blood pressure a bit borderline. It is better to lose a few kilograms than take tablets.


There have been other meta-analyses on weight loss and blood pressure [2, 3, 4], which are worth reading. They confirm a slightly higher response to reduced weight in people on antihypertensive medicines [2], and a general relationship between weight loss and reduced blood pressure [3].


Aerobic exercise may have effects on reducing blood pressure that are additional to those from any weight loss. An analysis of 53 randomised trials [4] in which treatment differences were limited to aerobic physical activity and control demonstrated an overall 4 mmHg reduction in systolic blood pressure and 3 mmHg in diastolic blood pressure when the overall weight change was virtually zero. The reduction tended to be larger with more exercise, and the only caveat was that some of the trials were small, and the small trials had a larger effect.


The clinical bottom line is that, for some people with borderline hypertension, there is a choice. Lose weight and exercise and feel younger and better, or take tablets that might make you feel dreadful. It should be a no-brainer.


References:

  1. JE Neter et al. Influence of weight reduction on blood pressure. A meta-analysis of randomised controlled trials. Hypertension 2003 42: e-publication.
  2. D Ebrahim, GD Smith. Lowering blood pressure: a systematic review of sustained effects of non-pharmacological interventions. Journal of Public Health Medicine 1998 20: 441-448.
  3. CD Mulrow et al. Dieting to reduce body weight for controlling hypertension in adults. Cochrane Database of Systematic Reviews 2000 2: CD000484.
  4. SP Whelton et al. Effects of aerobic exercise on blood pressure: a meta-analysis of randomised, controlled trials. Annals of Internal Medicine 2002 136: 493-503.

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