On 2009-03-13, Rich Billionaire wrote:

People keep saying it's safe to lose only 1 or 2 pounds per week,

Look up a paper called ``A limit on the energy transfer rate from the human fat
store in hypophagia''. This paper tries to answer the question: what is the
maximum amount of fat that can be lost by a dietary deficit, without loss of
lean tissue? The paper extrapolates the answer from some data, assuming the
maximum loss to be proportional to the size of the fat store, such that
each kilogram of fat can release provide 290+//25 kJ energy per day: it is
an inverse exponential process.

Translated to calories and imperial units, it's about 32 kcal per pound of fat.
32 kcal is about 0.8 percent of 3500, so another way to look at this is that
you can lose about 0.8% of your fat store per day, reducing it to 0.992. Over
seven days this is 0.992 to the power of 7, or 0.945. I.e. in a week, you can
lose 5.5% of your body fat by dieting, and it takes about 86 days to cut your
body fat in half.

For this to be a 2 pound loss, how much fat do you have to be carrying? 2 /
0.055 or about 36 pounds. But someone carrying 72 pounds of fat can double
that to 4 pounds per week. The necessary deficit might not be achievable
through diet alone (increased activity may be needed), but the fat store will
liberate the four pounds even without intense exercise.

E.g. suppose that you need 2000 calories per day to maintain your weight. The
most you can cut out by dieting is 2000 calories: eating nothing. That's a
non-starter. Now it may be that you have enough fat that 1500 calories can be
liberated from your fat store (e.g. you are carrying about 54 pounds of fat).
But that doesn't mean you should eat 500 calories per day; you will be
malnourished. Make the deficit from a combination of diet and exercise.
Exercise enough to burn, say, 1200 calories. Then your daily requirement is
3200 calories. Now if you consume 1700, you have a 1500 deficit.

Intense exercise may help if you are already so lean that the 5.5% weekly body
fat loss is too slow for you; you're no longer seeing results as fast as you
would like.