For what it’s worth, I think what’s really being inferred by the advice-giver is:
1 Granting your (advisee’s) starting point, you ought to lose weight.
2 Less calorie consumption and more calorie burning leads to weight loss.
3 Therefore you ought to consume less and burn more calories.
The advisee’s desire portrays the starting-point as a truth.
Perhaps so, but then the normativity stems from premise 1, leaving premise 2 as non-normative as ever. But the question is whether premise 2 could be a plausible reduction basis for normative claims.
For what it’s worth, I think what’s really being inferred by the advice-giver is:
1 Granting your (advisee’s) starting point, you ought to lose weight.
2 Less calorie consumption and more calorie burning leads to weight loss.
3 Therefore you ought to consume less and burn more calories.
The advisee’s desire portrays the starting-point as a truth.
Perhaps so, but then the normativity stems from premise 1, leaving premise 2 as non-normative as ever. But the question is whether premise 2 could be a plausible reduction basis for normative claims.