The rationale for the present study was that temporarily reversing the urbanization process in diabetic Aborigines should improve all aspects of their carbohydrate and lipid metabolism that are linked to insulin resistance. Ten full-blood, diabetic Aborigines from the Mowanjum Community (Derby, Western Australia) agreed to be tested before and after living for 7 wk as hunter-gatherers in their traditional country in north-western Australia. They were middle aged (53.9 +/- 1.8 yr) and overweight (81.9 +/- 3.4 kg), and all lost weight steadily over the 7-wk period (average, 8 kg). A detailed analysis of food intake over 2 wk revealed a low-energy intake (1200 kcal/person/day). Despite the high contribution of animal food to the total energy intake (64%), the diet was low in total fat (13%) due to the very low fat content of wild animals. Oral glucose tolerance tests (75 g glucose) were conducted in the urban setting and repeated at the end of 7 wk of traditional lifestyle. The marked improvement in glucose was due to both a fall in fasting glucose (11.6 +/- 1.2 mM before, 6.6 +/- 0.8 mM after) and an improvement in postprandial glucose clearance (incremental area under the glucose curve: 15.0 +/- 1.2 mmol/L/h before, 11.7 +/- 1.2 mmol/L/h after). Fasting plasma insulin concentration fell (23 +/- 2 mU/L before, 12 +/- 1 mU/L after) and the insulin response to glucose improved (incremental area under the insulin curve: 61 +/- 18 mU/L/h before, 104 +/- 21 mU/L/h after). The marked fall in fasting plasma triglycerides (4.0 +/- 0.5 mM before, 1.2 +/- 0.1 mM after) was due largely to the fall in VLDL triglyceride concentration (2.31 +/- 0.31 mM before, 0.20 +/- 0.03 mM after.(ABSTRACT TRUNCATED AT 250 WORDS)