In the UK, up to 5% of the general population is underweight, but more than 10% of those with lung or gastrointestinal diseases and who have recently had surgery. According to data in the UK using the Malnutrition Universal Screening Tool ('MUST'), which incorporates unintentional weight loss, more than 10% of the population over the age of 65 is at risk of malnutrition. A high proportion (10-60%) of hospital patients are also at risk, along with a similar proportion in care homes.
Unfortunately, metabolic compensation isn’t your body’s only strategy to prevent weight loss or encourage weight gain. Hunger hormones – leptin and ghrelin – are also at play. Fat cells produce leptin, which tells your brain when you’re full. Fat cells also shrink when you lose weight, producing less leptin and meaning you don’t feel as full. Strike one. Ghrelin, produced by the stomach, tells the brain it’s time to refuel. When you lose weight, ghrelin levels rise, prompting you to want to eat more frequently. Strike two. Research suggests that neither leptin levels nor ghrelin levels return to a normal baseline for at least a year.