So body fat is important because it causes inflammation, but not all your deposits are equally guilty. Fat under your skin – by far the most abundant type – is fairly benign, particularly on the lower body. Big thighs are not a worry (which means, incidentally, liposuction doesn’t make you healthier, even if it makes you less fat).
Fat around the organs in your abdomen, so called visceral fat, is dangerous, a reason doctors emphasise girth size, particularly for men. A degree of abdominal packing fat is normal, but the risk goes up sharply when normal levels are exceeded. The most ominous deposits are “ectopic” ones, which is fat where it is not meant to be, like inside the liver and around the heart.
So total fat is not so much the health issue as where, and the difference appears to come down to inflammatory behaviour. Abdominal and ectopic fat, for whatever reason, engage the inflammatory mechanisms more aggressively than skin deposits.
Food with added sugar appears to aggravate visceral fat, as does processed food generally, personal stress, and alcohol. Fibre like beans and vegetables improves it. Well known systems of healthy eating like the Mediterranean diet also improve it, and possibly there is more to it than energy; tentative evidence suggests specific contributions for antioxidant phytochemicals.
The good news is that dangerous fat is first to leave when asked. Healthy eating and exercise have the greatest effect on the worst deposits. Crucially, this means that body weight, although important, is not a reliable guide to how much good the right lifestyle choices are doing. The point is where, not just how much, and the scales do not tell you. Even if total weight is not shifting, doing the right things with diet and exercise will have crucial effects on fat distribution, and therefore the inflammation you walk around with every day.