Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or even a combination of these.[26][27] It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months[26][28] or 5% in the last month.[29] Another criterion used for assessing weight that is too low is the body mass index (BMI).[30] However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person.[31]
"When going out for fast food, I used to get the large-size value meal. Now, I satisfy a craving by ordering just one item: a small order of fries or a six-piece box of chicken nuggets. So far, I've shaved off 16 pounds in seven weeks, and I'm on track to being thinner than my high school self for my 10-year reunion later this year." —Miranda Jarrell, Birmingham, AL