In the effort to manage excess body weight, many people have experienced the ‘yo-yo’ effect: start a diet, weight goes down… end the diet, weight goes back up (and then some, in many cases). We already know that this fluctuation in weight is damaging to metabolism, in that our bodies essentially remember the highest weight we have ever had, making powerful hormonal and metabolic changes to drive us back up to our highest weight. Now, a study in the New England Journal of Medicine demonstrates that fluctuation in body weight is associated with a higher rate of heart attack and death in people who have coronary artery disease.
The study evaluated fluctuations in body weight amongst 9,509 people with heart disease, who were enrolled in the TnT trial of cholesterol medication atorvastatin, taking the opportunity to evaluate whether fluctuations in weight made a difference in terms of risk of having a cardiovascular event. In a post hoc analysis, they found that the greater the weight fluctuation, the higher the risk. Specifically, for every 1 Standard Deviation (SD) in weight, there was a 4% increase in risk for any cardiovascular event, and a 9% increase in risk of death, independent of other cardiovascular risk factors. Among patients in the top 20% for fluctuations in body weight, there was an 85% higher risk of a cardiovascular event and over a double increased risk of death, compared to those in the lowest 20% for fluctuations in body weight. The risk associated with weight fluctuation was higher in those with obesity or overweight, compared to those of normal body weight. Also, a greater body weight fluctuation was also associated with a higher risk of developing type 2 diabetes.
One wonders whether these findings could simply reflect that people who had wide fluctuations in weight were sicker in general (eg big weight loss with illness), though this clinical trial did exclude people with a poor prognosis. The study also did not assess whether the weight fluctuations were intentional (eg dieting) vs unintentional (eg illness).
We cannot infer causality from this study – in other words, we can’t be sure that the weight fluctuations were the cause of the increased cardiovascular events – but the association between weight fluctuation and cardiovascular events was nevertheless strong. Given these findings, it seems more important than ever to avoid yo-yo weight changes by making permanent lifestyle changes rather than engaging in temporary solutions/programs to optimally manage weight.