I'm a 5"10, 77kg, 25 year old man. if i cut calories by 600 below my daily needs what fat to muscle loss ratio can i expect per week. i don't exercise or intend to at this point. i know it's a difficult question but an estimate will be fine?

No consistent ratio: The ratio of fat to muscle loss with any given calorie deficit depends partly on the nutritional composition of your diet. You need the proper balance of unrefined carbs, high quality protein and some fat to avoid muscle loss & maintain stable blood sugar levels. Regardless, weight training is ESSENTIAL to maintaining muscle mass. See >hsph.harvard.edu/obesity prevention

See answer: I couldn't find a quick answer but the following may be helpful. The ratio is probably variable. An obese patient will loose a higher percentage of fat and loose less muscle than a thin patient. You can reduce your muscle loss by eating enough protein, limiting weight loss to to 1.5-2 pounds a week and do muscle strengthening exercises which appear to reduce muscle loss.

Best to exercise: To answer your question,that is a deficit of 4200 calories par week. On the average 3500 calorie deficit should cause 1pound of fat loss,You also lose water weight giving an appearance of more weight loss than 1pound. Hence take in adequate amounts of water while on any diet. Exercise has cardiovascular benefits, Keep moving

Cut calories: 600 cal will be 66.67 gram of fat. and will be equal to 150 gram of protein (muscle).your wt now 169 .4 Ibs and your ideal wt should be 166 Ibs. to me you are lean..there is no much fat to lose ( only 3.4 Ibs.or 1.5 Kg). and if you cut the 600 cal. they will come from your fat first (in 22 days) and after this from the muscle. I hope I answered your question