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Ten men keeping food and activity diaries for 60 days illustrated the relationship between food energy intake and the activity pattern. During the first 30 days the men ate normally. During the second 30 days the men voluntarily ate a restricted diet with an average deficit of 500 kcal/day. The food energy intake deficit was created by prohibiting calorically dense fats and refined sugars and encouraging consumption of high-volume-to-calorie foods such as grains and cereals. The men were unable to adjust to the higher volume of food required to maintain their usual food energy intake. The major activity pattern changes during the restricted-intake phase were: a reduction in standing at leisure of 12 min/day (p < .0001); a reduction in walking of 17.2 min/day (p < .0001); and an increase in sitting at leisure of 18.9 min/day (p < .003). No significant change in studying or sleeping was observed. Thus, the activity pattern was modified. Lower-effort discretionary activities were substituted for higher-effort discretionary activities. Obligatory activities were not affected.