Fasting, the first two days you burn mainly muscle. So, how does dieting work?

How do people lose FAT when they diet?
Through just reduced caloric intake, as opposed to 2+ day fasting.


Actually, you burn glycogen. For every gram of glycogen, you also lose 4 grams of water that is bound with it.

Even at full glycogen depletion, you derive appx. 15% of your calories from muscle.

Exactly, glycogen and the associated water loss dominate on the first few days of a fast. Here’s a link to a graph showing the composition of weight loss over 30 days of fasting:

Awesome, so uh…how does that work with just day to day dieting then?
Is glycogen and water loss the main way people lose weight?
When does the fat loss start?
If, during a fast, the first 2-3 days are just glycogen and water.


Typical glycogen storage is only about 350-450 grams-1 pound or less. Once that’s burned, rate of weight loss drops way off.

A high protein diet can help minimize muscle loss(so does exercise) while fat loss should be the primary loss of weight.

Remember that fat is very calorie dense so even a decent caloric deficit will only result in a small daily loss-generally 1-2 lbs a week is safe.

Look at it this way -

The body mainly uses glucose for energy and maintains the blood sugar level within a fairly narrow range. Glycogen is stored sugar and is the main means of keeping those levels stable. It’s pretty quick to be tapped and can provide and buffer a fair amount of glucose pretty fast. You can deplete those stores pretty much completely pretty fast and rebuild them pretty quickly as well once glucose sources in excess of what is needed for immediate use are provided.

Fat can only provide energy in a relative dribble, it can just keep doing it for a long long time. Protein a bit faster but still not anywhere as quick to get at as glycogen.

Run a moderate deficit and you will deplete your glycogen stores to some degree during the day (such as during exercise) and use your fat stores along the way too. You will then replete those glycogen stores from intake, using fat for more of the lower metabolic demands of the rest of the day.

Fasting or gradual moderate restriction of calories with increased activity fat loss can only be so great per day. (Possibly a little bit faster with some HIIT thrown into the mix … maybe.) So the answer to the op of “How do people lose FAT when they diet?” is “Gradually.”

When you burn glycogen…where is it? Physically? I mean, are you pulling it out of the bloodstream, or fatty tissue, or muscle, or cerebral neurons, or…?

I am guessing it changes over time; at first from the bloodstream, later from other tissue. But I dunno, so am asking.

(Where does the water come from, too?)

Primary stores are in the muscle and liver cells.

The water is bound to the glycogen at time of storage. When the glycogen is burned, the water is released into the body to be excreted in sweat, urine or respiration.

If you maintain a decent caloric intake (not starvation-level) and do some reasonable weight-training, you can encourage your body to drop fat instead of muscle. Dieting will typically result in some muscle loss, but it’s possible to minimize that if you get adequate nutrition and weight-bearing exercise.

That’s why I fell in love with bodybuilding; it’s the science/art of burning as much fat as possible while simultaneously preserving as much lean body mass as possible. The longer I am involved with bodybuilding, the more I realize just how little I understand about the human body.

Anyone heard of Primal Blueprint or Paleo? Opinions…

They are among the nutrition plans that overall do better than traditional modern Western fare. Of course those who are the plans’ acolytes often take the position (stridently) that it is the best or only approach to take … which is silly. Plus much of what these folks do under the guise of “paleo” is scarcely in the wide range of what ancestral humans ate, either in the specifics or in the macronutrient balance. (Modern beef is much much higher in total fat, especially saturated fat, and lower in omega 3s and MUFAs, than the game meats, fish and fowl that the variety of ancestral diets were commonly heavy in.) Some of them are merely using “Paleo” to justify eating a high fat/low carb diet … which makes no comment on whether or not it is an effective approach for them.

If Paleo means little refined carbs; lots of nuts, seeds, veggies, fruits; relatively high protein with a fair amount of omega 3s, MUFA and PUFAs (such as from fish fowl and game meats or other sources that replicate that balance) then I personally think that’s mighty fine eatin’ that happens to also be pretty healthful. When it means bacon, fatty beef, chicken wings fried in lard … I’d have my doubts on both fronts.


I understand that modern beef (feedlot, lots of standing around getting fat) is off the table lol, grassfed is the beef of choice. All meat for that matter.

According to at least one study, it isn’t red meat but processed red meat that is really bad for you (I don’t really worry either way since my family doesn’t have any history of CVD, which is more genetics than diet, although I rarely eat processed meat). What they mean by processed meat however, they don’t say, other than give examples, like hot dogs (most likely any meat that isn’t in a “natural” state and contains additives like sodium nitr(ate/ite), which has also long been know to increase cancer risk):

Of course, the same goes for vegetarian foods as well (you know, what some refer to as “food-like products”); many grains have an extreme ratio of omega 3:6, far in excess of anything considered to be healthy (and actually, so do many other foods considered to be healthy; not worth getting grass-fed beef (which is also similar to chicken in the ratios) according to this, or most nuts, as they say, eat fish or fish oil if you want more omega-3).

Also, the thinking regarding saturated fat, like cholesterol, is changing; for example, this study finds that replacing saturated fat with carbohydrates **increases **CVD risk, at least for people who already have high triglycerides/cholesterol/blood pressure:

There’s a more detailed discussion in this thread.