Asked by: Annie Martoni, by email
Within one or two days of your last meal, your body will have exhausted all the glycogen stored in the liver and muscles. Most of your energy requirements will be met by breaking down stored fat into ketones, but brain cells and red blood cells can't metabolise ketones, so their glucose requirements must be met by breaking down muscle.
Even if you have lots of body fat left to burn, you can still starve to death if you don't have enough muscle because vital muscles like the heart will have been weakened to the point where they stop working. For this reason, doctors normally consider 40 to 50 per cent weight loss as life-threatening, regardless of your initial body weight.
Total starvation is normally fatal in eight to 12 weeks. In less extreme cases, however, where you are still receiving some calories - particularly if these calories include a high proportion of protein - being fat will help you survive much longer, because your body will be able to meet the majority of your calorie requirements from stored fat.
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As an expert in human physiology and nutrition, I can confidently provide insight into the concepts discussed in the article. The information presented revolves around the intricate processes the human body undergoes during periods of fasting or starvation, shedding light on the critical role of glycogen, ketones, and the preservation of muscle mass for survival.
Firstly, within one or two days of consuming a meal, the body depletes its stored glycogen found in the liver and muscles. This depletion initiates a shift in the primary energy source from carbohydrates to stored fat. The breakdown of fat results in the production of ketones, which serve as an alternative fuel for most bodily functions. However, crucial tissues such as brain cells and red blood cells cannot directly metabolize ketones, necessitating the breakdown of muscle tissue to meet their glucose requirements.
The article emphasizes the importance of muscle preservation during periods of starvation. Even if an individual possesses ample body fat reserves, the depletion of muscle mass can lead to life-threatening consequences. The vital organs, particularly the heart, may weaken to a point where they cease to function effectively, highlighting the significance of maintaining muscle integrity for overall health and survival.
Medical professionals typically identify a 40 to 50 per cent weight loss as a critical threshold, irrespective of an individual's initial body weight, signaling a life-threatening condition. The article further underscores the grim reality that total starvation is generally fatal within eight to 12 weeks.
In less extreme cases, where individuals still receive some calorie intake, especially those derived from a high proportion of protein, the body's ability to utilize stored fat for energy becomes crucial. Being overweight, in this context, can provide a survival advantage, as the body can meet a significant portion of its calorie requirements from stored fat.
In summary, the concepts discussed in the article highlight the intricate interplay between glycogen depletion, ketone production, muscle breakdown, and the role of body fat in sustaining life during periods of caloric restriction. The information serves as a testament to the body's remarkable adaptability and the physiological challenges it faces when subjected to starvation.
