First hand experience with Starvation Mode.

you say you're approaching disordered eating... take that as a red flag. What do you hope to achieve from this thread? Justifcation to carry on eating way too little?

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"Starvation mode" is a stupid term people use to refer to several changes that can occur in the human body (including behavioural changes) in response to eating too little. There's no "on/off" switch in your head called "starvation mode" - the longer you eat too little for, the more of these things change in ways that make it difficult to stick to a diet long term, or if you're determined enough to carry on eating way too little, will compromise your health

short term changes may include:
- obsessing about food
- increased appetite (sometimes extremely increased)
- appetite shutting down then coming back with avengence leading to binge eating
- binge eating
- feeling tired and run down/lacking energy

medium term changes:
- your body using lean mass as fuel to make up the deficit to preserve fat stores for longer, which results in the metabolism slowing because the muscle cells you've lost no longer require the energy they were using to stay alive
- adaptive thermogenesis - this is further slowing of the metabolism that's not explained by body composition changes. This happens because your body tries to deal with the food shortage by directing less energy into non-essential functions, so you end up feeling cold all the time (less energy is spent heating you), your hair and skin look dull and your hair may fall out (less energy is being invested in keeping your skin and hair healthy), you have menstrual disturbances and your menstrual cycle may stop altogether (less energy being invested in reproduction, or even the reproductive system shutting down altogether), and similar, throughout the body. The result is the body saves energy, but your health deteriorates.
-rebound fat gain if you binge (likely) or start eating normally again, due to a combination of your metabolism slowing and increased hunger (which may come out of nowhere while your hunger signals are switched off for much of the time)

long term changes:
- if the food shortage is really extreme, when your skeletal muscles and fat stores have all been used up keeping you alive, your body then metabolises your organs for energy. Death from multiple organ failure usually follows this.
- if the food shortage isn't extreme enough for you to starve to death, your body may get to the point where it's burned off enough muscle tissue and done adaptive thermogenesis enough that your low number of calories is now maintenance. At which point you have poor health and all the health risks associated with being underweight and eating too little, yet eating more will result in fat gain. Note that it is possible to get your body out of this state through eating loads and doing exercise to rebuild your muscles,
- it's hit and miss whether your body reaches this equilibrium first or starves to death first. Usually the calories taken in from binge eating or phases of overeating between the starve cycles to prevent people from starving to death, however this is all going to be stored as fat, and the result is "normal weight obesity" where the person's weight is in the healthy BMI range but their body fat percentage is in the obese range, and their skeletal muscle is wasted away and their bone density is low. With this you have both the health risks of a high body fat percentage combined with the health risks of being underweight (e.g. osteoporosis)

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My advice is get help for your disordered eating and stop looking for justification to carry on with it. "starvation mode" is a stupid term, but your body does adapt in ways that are counterproductive for long term success at dieting and bad for your health if you eat too little, especially if you eat too little for prolonged periods or intersperse starvation cycles with overeating or binge eating. So please just stop eating too little and get help for your disordered eating if you need to.

The thing that annoys me about starvation mode being bandied around on sites like this is the way it trivialises true starvation mode - you know, people in famine areas in the third world who literally starve to death.
Although very few people ever actually starve to death - what happens is that their emancipated bodies are so malnourished and so weak that they die of things like pneumonia and infective diahrroea ( needless to say, such people do not have access to antibiotics etc)

Unless you have a mental illness causing extreme anorexia, you are not going to face starvation in first world countries.

If you are posting on this site, you have electricity and Internet access - you are not somewhere where people are facing starvation mode.