Objective: The objective of the present study was to elucidate the separate effects of energy restriction and weight loss on blood pressure (BP) and to assess the relationship between sodium intake, weight loss, and BP.
Methods: Two hundred and eight overweight and obese subjects (age: 52.4 +/- 0.8 yrs; BMI 33.6 +/- 0.3 kg/m(2)) completed a weight loss diet program consisting of 8-12 weeks of moderate energy restriction (ER; approximately 30% energy deficit, unrestricted salt intake) and four weeks of energy balance (EB). Body weight and BP were measured at baseline, the midpoint, and the end of ER and after EB. 24-hr Na+ excretion was measured at baseline and at the end of EB.
Results: Overall, body weight reduced progressively by 7.0 +/- 0.2 kg (7.5%; p < 0.001) with the hypocaloric diet. BP fell substantially during the first phase of ER (-5.7 +/- 0.7/-2.6 +/- 0.4 mmHg, p = 0.001), corresponding to a 4.5 +/- 0.2 kg weight reduction, with no further BP changes during the second phase of ER, despite further weight loss (2.4 +/- 0.1 kg). During EB, BP remained stable. The hypotensive effects of caloric restriction and weight loss were similar across clinical subgroups defined by age, sex, diabetes, insulin sensitivity, and hypertensive status. BP responses to weight loss were independent of 24-hr urinary Na+ excretion. 24-hr urinary Na+ excretion was similar at baseline and at the end of EB (146.5 +/- 5.3 vs. 146.9 +/- 5.3 mmol/24-hr).
Conclusion: The hypotensive effects of caloric restriction do not rebound upon return to eucaloric intake at a reduced body weight, and a high sodium intake does not appear to alter the hypotensive effects of weight loss. This reinforces the clinical importance of weight loss and supports the recommendation that strategies for promoting long-term weight loss should become the primary focus of dietary efforts to control BP in overweight patients.