For some people there’s no such thing as moderation. Despite mountains of data-supported evidence, diets that offer only short-term results but do long-term damage continue to capture followers. The problems are not limited to disordered thinking about food. The internal organs, hair, skin and nails can also suffer depending on the caloric and nutrient levels of the particular diet and how long a person remains on it. Celebrities can get away with doing these diets in short cycles because they have an army of skincare specialists to replace what’s lost and to smooth away dead cells. Others might not have the means to repair the damage.

When you drop below 1,000 calories a day for more than a few weeks, your nutrient levels drop accordingly and with them, your hair and skin. As your body becomes deprived, it no longer has the necessary fuel to regenerate healthy cells. The result is dry, flaking skin and thinning hair. As time goes on, this problem will only get worse, with dieters developing rashes and lesions that, contrary to the claims of detox proponents, are not the result of your body ridding itself of toxins. It is, rather, a surfeit of dead skin cells, lack of cell turnover, and a lack of necessary oils.

Extremely low-carb diets, which have somewhat fallen out of favour, send your body into a state called ketosis; you might get skinny, but your skin will lack a certain glow and you have a large chance of developing a rash commonly associated with ketosis and generally dry skin all over.

Hair loss caused by such dieting can be reversed once a person returns to eating normally, but skin damage can be longer lasting. As we age, our collagen level drops, so our skin will not just bounce back from a period of extreme dryness or damage. In addition, rashes and irritation can cause hyperpigmentation that is hard to get rid of without laser treatments or bleaching (which can bring its own set of complications).

Get back to what your nan always told you: All things in moderation, withextra moderation when it comes to processed grains and sugars. The foods you need for great skin are always to be found in the oft-cited categories of fruits and vegetables of almost all types, with a special nod to nuts, nut butters, avocado, and olive oil for the vitamin E they bring. You can easily build a healthy and balanced diet that will allow you to lose weight, maintain your energy, and get good skin. In any case, if you need to lose more than 25 kilos, you should be doing so under medical supervision to ensure that you get the nutrients you need and can consult someone familiar with your diet to diagnose problems as they arise.