In open prospective monocentric study in 3 parallel groups we studied the effectiveness of correction of body composition using low calorie diet therapy with inclusion of specialized food products (SFP)--sources of polyphenols and iridoids made on the basis of the juice of Morinda citrifolia L. fruits. We studied 90 patients aged from 30 to 50 years old with grade III obesity and clinically expressed secondary diastolic heart failure. The duration of diet therapy was 42 days. It was shown that low-calorie diet has non-optimal effect on the body composition in morbidly obese patients with secondary diastolic heart failure, namely leading to the expressed loss of body fatless (7.2%, p=0.00008) and muscle mass (by 16.6%, p=0.00004); at the same time the reduction of total body weight is noted only by 2.3% (p=0.053), reduction of waist measurement by 1.3% (p=0.028) and reduction of hips measurement by 1.3% (p=0.09), accompanied by the reduction of body fat by 8.5% (p=0.000017) and of liquid by 7.3% (p=0.0018). The introduction of the SFP into the diet optimizes the effect of low calorie diet therapy on the anthropometric parameters and body composition. The most important effect of the SFP is the ability to prevent the excess loss of muscle mass in patients, and this effect is being dose-dependent. The loss of muscle mass in two groups of patients was 3.1-4.1% after 6 weeks of diet therapy, while in the control group it was 8.5% (p=0.0051). We have concluded that the inclusion of the SFP, manufactured on the basis Morinda citrifolia L. (noni) juice to the low calorie diet allows to initiate mainly the loss of the body fat with the simultaneous protection of active cellular mass, which is without doubt can be considered as the advantage compared to the standard low calorie diet.