About a decade ago, a huge outcry over studies that showed Bisphenol A, or BPA, a chemical compound used in plastic to make it tough, was an endocrine disruptor and could cause changes to breasts, testicles, brains, and body size, including upping the risk for abdominal obesity. People in love with their Nalgene bottles—which, at that point, contained the chemical at that point—tossed them away and switched to stainless steel or glass bottles until companies began offering BPA-free plastic bottles. Now you won’t find it around as much, as it’s been replaced by two other chemicals: Bisphenol F (BPF) and Bisphenol S (BPS).

Those similarly named chemicals don’t seem like they would be much different to BPA, but a new study from the University of Iowa showed that they don’t contribute to increasing gut size significantly. The researchers looked at data from a Centers for Disease Control study which, like some past studies, determined that BPA was indeed linked to increased obesity in people. The new chemical formulations, however, were not associated with abnormal weight gain in the data they looked at.

The study authors state that even though BPA is linked to obesity, and concentrations of BPF or BPS were not found to contribute to obesity in the study, “whether BPF and BPS at the same population exposure levels as BPA pose an increased risk of obesity is not known. Additionally, BPA has only been substituted with BPF and BPS in the past two decades.”

We suggest limiting your exposure to any of the chemicals as much as possible, and trading your plastic water bottles for stainless steel ones from companies like Miir, Contigo, and Hydro Flask. The double-walled steel containers keep your daily hydration dose colder (or blast of coffee hotter) than plastic, and, while not as light, are more durable and longer-lasting.