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"A shot of reality" painted a necessary picture of the problem of short-term weight-loss solutions. However, the link between being overweight and serious negative health outcomes remains questionable. Relatively recent evidence suggests there is no difference in mortality risk until either end of the BMI scale, with people in the "overweight" category having the healthiest …

Dan Levitt writes about the issue of cognitive bias in science. Certainly, most researchers have a problem with this that can adversely affect their work. Most would admit, perhaps with embarrassment and annoyance, that they missed something in the belief that "it couldn't work" ( 5 August, p 21 ). However, the problem is endemic …

I have to disagree with Levitt on one point. In my field, cell biology, he claims that the interior of the cell, the cytoplasm, was believed to be just a "biochemical bog" a century ago. But chloroplasts, organelles that carry out photosynthesis in plant cells, were discovered far earlier than that. Mitochondria, the so-called powerhouses …

Cooling turtle nests with a bit of cold seawater, in order to shift the temperature-dependent sex ratio of the resulting hatchlings, is an intriguingly simple solution to the misalignment of this system due to climate change ( 29 July, p 16 ). However, there is a risk to this strategy that isn't mentioned: it would …

When it comes to climate change, our roofs are considered part of the problem and part of the solution. My house is topped with Welsh slate, which I estimate absorbs more than 80 per cent of incident solar radiation. On a sunny day, it heats up dramatically and, of course, re-radiates the absorbed energy at …

Bravo for Grace Wade's analysis on "ultra-processed" foods, which questions the presumption that they are always harmful. I am glad to see New Scientist finally addressing the question of whether we can simply blame these foods for health problems, as though the ultra-processed term is well-defined and they are all bad ( 19 August, p …

Georgina Skipper is quite right, herring gulls are the intellectual equals of corvids in many respects. I observed them on Margate beach in the UK dropping crustaceans and molluscs to access the contents well before carrion crows hit the news for similar activity. The persistence of the gulls was remarkable ( Letters, 12 August ). …

Your report on the net energy gain from a fusion reaction in the US repeats the fallacy that a nuclear fusion power plant would produce no radioactive waste ( 12 August, p 13 ). The deuterium-tritium fusion reaction, currently the focus of fusion energy experiments, produces high-energy neutrons. These hit the containment vessel, blanket and …

Jason Arunn Murugesu rightly laments that we use too much water. However, there is an elephant in the room to address. Household water consumption is entirely drinking water. Why do we use drinking water for toilets? Used water, for example from showering, would still be perfect for re-using in the toilet ( 29 July, p …

Pete Drake is right to say that we could calculate personal carbon footprints by trawling everyone's financial transactions, though it is harder than he thinks ( Letters, 12 August ). But we could get the same effect by adopting the plan of the Green Party of England and Wales. Its proposed carbon tax would apply …