以下摘自life App The Five Stages of Intermittent (and Prolonged) FastingBy 12 hours, you’ve entered the metabolic state called ketosis (Anton et al., Obesity 2018). In this state, your body starts to break down and burn fat. Some of this fat is used by the liver to produce ketone bodies (ketones). The two main ketones, acetoacetate and β-hydroxybutyrate (BHB), serve as an alternative energy source for the cells of your heart, skeletal muscle, and brain, when glucose isn’t readily available. Did you know that your brain uses up some 60% of your glucose when your body is in the resting state? During intermittent fasting, ketone bodies generated by your liver partly replace glucose as fuel for your brain as well as other organs. This ketone usage by your brain is one of the reasons that intermittent fasting is often claimed to promote mental clarity and positive mood – ketones produce less inflammatory products as they are being metabolized than does glucose, and they can even kick-start production of the brain growth factor BDNF! Ketones have also been shown to reduce cellular damage and cell death in neurons and can also reduce inflammation in other cell types. By 18 hours, you’ve switched to fat-burning mode and are generating significant ketones (Anton et al., Obesity 2018). You can now begin to measure blood ketone levels above your baseline values. Under normal conditions, the concentration of ketones in your plasma ranges between 0.05 and 0.1 mM. When you fast or restrict the carbohydrates in your diet, this concentration can reach 5-7 mM. You can help accelerate ketone production with some heart-pumping exercise! For example, intermittent fasting combined with running cause rewiring of nerve cells in the brain which leads to improved learning and memory in lab animals As their level in your bloodstream rises, ketones can act as signaling molecules, similar to hormones, to tell your body to ramp up stress-busting pathways that reduce inflammation and repair damaged DNA for example. Within 24 hours, your cells are increasingly recycling old components and breaking down misfolded proteins linked to Alzheimer’s and other diseases (Alirezaei et al., Autophagy 2010). This is a process called autophagy. Autophagy is an important process for cellular and tissue rejuvenation – it removes damaged cellular components including misfolded proteins. When your cells can’t or don’t initiate autophagy, bad things happen, including neurodegenerative diseases, which seem to come about as a result of the reduced autophagy that occurs during aging. Intermittent fasting activates the AMPK signaling pathway and inhibits mTOR activity, which in turn activates autophagy. This only begins to happen, however, when you substantially deplete your glucose stores and your insulin levels begin to drop. Intermittent fasting is one way in which you can increase autophagy in your cells and possibly reduce the effects of aging. A 2019 study with 11 overweight adults who only ate between 8 am and 2 pm showed increased markers of autophagy in their blood after fasting for around 18 hours, compared to control participants who only fasted for 12 hours. A second study detected autophagy in human neutrophils starting at 24 hours of fasting. In a third study, skeletal muscle biopsies of healthy male volunteers who fasted for 72 hours showed reduced mTOR and increased autophagy. In mice deprived of food, autophagy increases after 24 hours and this effect is magnified in cells of the liver and brain after 48 hours. But intermittent fasting is not the only way to enhance the ability of your cells to recycle old components. Some of the known benefits of exercise for overall health have to do with increased autophagy. For example, autophagy induced by exercise delays the progression of heart disease by giving the heart better quality cell parts and reducing oxidative damage. Exercise, just like intermittent fasting, inactivates mTOR, which increases autophagy in many tissues. Exercise mimics the effects of going without food for an extended period: It activates AMPK as well as autophagy-related genes and proteins. In mice, endurance exercise increases autophagy in the heart, liver, pancreas, fat tissue, and brain. In humans, autophagy increases during high intensity exercise, including marathon running and cycling. By 48 hours without calories or with very few calories, carbs or protein, your growth hormone level is up to five times as high as when you started your fast (Hartman et al.,1992). Part of the reason for this is that ketone bodies produced during fasting promote growth hormone secretion, for example in the brain. Ghrelin, the hunger hormone, also promotes growth hormone secretion. Growth hormone helps preserve lean muscle mass and reduces fat tissue accumulation, particularly as we age. It also appears to play a role in mammalian longevity and can promote wound healing and cardiovascular health. By 54 hours, your insulin has dropped to its lowest level point since you started fasting and your body is becoming increasingly insulin-sensitive (Klein et al., 1993). Lowering your insulin levels through Intermittent fasting has a range of health benefits both short term and long term. Lowered insulin levels put a brake on the insulin and mTOR signaling pathways, activating autophagy. Lowered insulin levels can reduce inflammation, make you more insulin sensitive (and/or less insulin resistant, which is especially a good thing if you have a high risk of developing diabetes) and protect you from chronic diseases of aging including cancer. By 72 hours, your body is breaking down old immune cells and generating new ones (Cheng et al., 2014). Prolonged fasting reduces circulating IGF-1 levels and PKA activity in various cell populations. IGF-1, or insulin-like growth factor 1, looks a lot like insulin and has growth-promoting effects on almost every cell in the body. IGF-1 activates signaling pathways including the PI3K-Akt pathway that promotes cell survival and growth. PKA can also activate the mTOR pathway (and, of interest, too much caffeine during a fast may promote activation of PKA). You might see where this is leading – pressing the brakes on IGF-1 and PKA through nutrient restriction and fasting can turn down cellular survival pathways and lead to breakdown and recycling of old cells and proteins. Studies in mice have shown that prolonged fasting (greater than 48 hours), by reducing IGF-1 and PKA, leads to stress resistance, self-renewal and regeneration of hematopoietic or blood cell stem cells. Through this same mechanism, prolonged fasting for 72 hours has been shown to preserve healthy white blood cell or lymphocyte counts in patients undergoing chemotherapy.
饿的感觉半小时就会消失的。
胰岛素抵抗了
妹子，能具体说说脂肪消耗啥感觉么？谢谢
查了一下。那就是糖前？
太慢了不行。一定要有运动量，判断的标准是要让自己气喘吁吁。就是要有速度，最好是跑得自己上气不接下气，大汉淋漓。可以先跑10分钟让自己warm up，然后加速，让心快加速，自己气喘厉害，坚持至少10分钟，然后慢下来跑几分钟，再坚持快速10分种，在慢下来几分钟，接着再来个10分钟。一周坚持3-4次，不可能不降体重。但是刚开始这样跑会腿酸，要用滚筒按摩，把肌肉放松。坚持半年，看效果。另外饮食是不饿不吃，饿了吃到不饿为止。多吃水果蔬菜。
太慢了不行。一定要有运动量，判断的标准是要让自己气喘吁吁。就是要有速度，最好是跑得自己上气不接下气，大汉淋漓。可以先跑10分钟让自己warm up，然后加速，让心快加速，自己气喘厉害，坚持至少10分钟，然后慢下来跑几分钟，再坚持快速10分种，在慢下来几分钟，接着再来个10分钟。一周坚持3-4次，不可能不降体重。但是刚开始这样跑会腿酸，要用滚筒按摩，把肌肉放松。坚持半年，看效果。另外饮食是不饿不吃，饿了吃到不饿为止。
给你推荐Two Meals a Day，系统的了解一下