As anticipated, women who lost weight over one year were more likely to reduce or eliminate their hot flash or night sweat symptoms compared with those who maintained their weight. Additionally, women who participated in a dietary modification trial that encouraged them to decrease fat and increase fruit, vegetable, and whole grain intake, were significantly more likely to eliminate VMS. The effects were statistically significant and independent though the association of weight loss and elimination of VMS appeared somewhat stronger in the DM-I arm. The surprising finding that women in the intervention who gained >10 lbs also reduced VMS suggests that the beneficial impact of healthy diet was not restricted to those who lost weight. Adjustment for factors known to be related to VMS did not explain associations. This is the largest report to date of the effect of weight loss on change in vasomotor symptom status, and the first trial to examine the influence of a healthy dietary change on VMS changes. These findings suggest that weight loss and healthy dietary changes could each help to reduce or eliminate VMS.
We report similar findings for weight loss and VMS to those in another trial of weight loss and hot flashes 28
. However, that study was limited because it included only women with urinary incontinence. This study is considerably larger and should generalize more broadly to the population of postmenopausal women. Given the possible adverse effects of hormone therapy on breast cancer and cardiovascular disease risk, intentional weight loss following a healthy diet may be an important, alternative means of reducing VMS without exacerbating risk of disease.
Diet also appeared to reduce VMS beyond the effects of weight change. Although analyses suggested the potential benefit of weight loss with regard to VMS in both the DM-I and control groups, the association between weight loss and elimination of symptoms appeared stronger in the intervention group. Interestingly, the beneficial effect of diet on VMS also appeared among DM-I participants who gained weight. Though weight gain occurred less often in the intervention than in controls, we considered that weight gain in the intervention could have resulted from an increased intake of fruit, vegetables, and whole grains without a commensurate reduction in fat intake. However, in post-hoc analysis, women in the DM-I who gained weight reported significant reductions in fat and increases in carbohydrate (but not protein) intake, although those who lost weight had greater changes than those who maintained or gained weight. At the end of year 1, compared with the controls, women in the intervention had higher intakes of fiber (17.9 vs. 14.9 g/d), fruit (2.5 vs. 1.8 s/d), vegetables (2.6 vs. 2.1 s/d), genistein (0.73 vs. 0.65 mg/d) and vegetable protein (21.4 vs. 19.0 g/d) and lower intake of total fat (24.7 vs. 34.9% of kcal) and Ω-3 fatty acids (1.1 vs. 1.5 g/d) (all differences, p<0.05). Stratifying by weight change and comparing women in the DM-I with the controls, there were differences in fat intake in all weight categories and differences in vegetable, vegetable protein, and fiber intake among those who lost weight, maintained weight, or gained a small amount of weight (all differences, p<0.05), but not among those who gained a medium or large amount of weight (data not shown). However, no differences in dietary components or changes could explain the apparently stronger effect in DM-I women who gained vs. maintained weight and this result may be due to chance. Additional research is needed to evaluate the aspects of diet that reduce VMS.
An alternative explanation, the placebo effect, i.e., the increased well-being due to the positive healing attention provided by nutritionists to women in this intervention39
, may explain some of the intervention’s effect on this subjective outcome 40
. Related to this but aside from the direct social benefit of the intervention, it is possible that engagement in the intervention augmented feelings of empowerment associated with one’s own attempts to improve one’s health 41
which could diminish VMS 42
. Feelings of taking control of one’s diet and thus one’s health could help to explain the suggested benefit among controls who lost substantial weight as well as the suggested benefits in the intervention group, regardless of weight change.
Although models employing the full sample suggested benefit across the range of VMS, in analyses restricting to those with VMS at baseline, the greatest benefits accrued to those with mild, rather than moderate or severe VMS. In a sensitivity analysis, we evaluated whether more extreme weight changes might influence associations. In an analysis of weight change in kilograms, comparable to the analysis of weight change in pounds, we noted an increased odds of eliminating symptoms (OR=2.36, 95% CI: 1.14–4.92) among those with moderate or severe symptoms at baseline who lost ≥10 kg (~22 lbs), compared to those who maintained weight within 5 kg (~11 lbs). In fact, women who were most likely to see relief of their symptoms lost a substantial amount of weight—10% or more of their baseline weight, suggesting the possible need to lose considerable weight for this strategy to succeed. Given that the average weight among overweight women was 79.2 kg (~175 lbs), a woman of this weight who has moderate or severe symptoms may need to lose at least 7.92 kg (17.5 lbs) to clearly experience an effect. However, this weight loss should ideally be a loss of fat and not lean mass.
With regard to treatment, reduction in severity of symptoms and not simply the elimination of symptoms would be considered desirable. Nevertheless, although small weight or dietary changes may make little measurable difference in severity of symptoms, larger changes may bring substantial relief. Both weight loss and diet reduced symptoms over the course of a year. Given that 2/3 of the population is overweight, weight loss and healthy dietary changes could be broadly useful strategies for reducing VMS in addition to improving other health outcomes.
Proposed mechanisms for weight and VMS include greater insulation against heat loss due to increased peripheral fat43
, abnormal sympathetic neural activity associated with increased visceral fat44
, and alterations in leptin and other cytokines expressed by adipocytes that affect thermoregulatory function 45
. Women who are overweight or obese may also differ with regard to social or psychological46
factors that affect subjective experience of somatic symptoms. Our results for weight loss and VMS are consistent with the thermoregulatory model and suggest that weight loss may reduce adipose tissue, a potent insulator 47
, and may thus reduce VMS because of the reduced need to dissipate excess body heat that occurs in the context of the menopausal transition 48, 49
. However, further research is needed to evaluate mechanistic relationships between diet and VMS.
Study strengths include a large sample size in a well-characterized cohort of postmenopausal women and the ability to control for numerous covariates. Because of longitudinal assessment, we were also able to assess changes in VMS over time. While we report on subjective and not objective measures of hot flashes and night sweats, a woman’s perception of the bother of symptoms is a valid indicator of symptoms 50
. We did not measure data on frequency of hot flashes or night sweats, a common measure in assessment of VMS. We had limited statistical power to fully examine the influence of diet and weight change, particularly on those with moderate to severe symptoms. Women were not selected for the trial based on bothersome vasomotor symptoms, so future clinical trials should focus on this population.
In summary, women who lost weight during participation in a dietary modification trial designed to reduce fat and increase fruit, vegetable, and fiber intake reported a reduction or elimination of VMS over one year. The dietary intervention appeared to ameliorate symptoms over and above the effect of weight change. These results support the use of weight loss and healthy dietary change as alternative approaches to hormone therapy for the relief of vasomotor symptoms.