The purpose of this study is to minimize the loss of lean body mass that occurs during a weight-loss program in obese people by changing the nature of ingested protein and the pattern of protein feeding

In most physiological situations, the adequate amount of protein necessary to promote health is more and more well known. However, for an adequate protein intake, it was shown that the kinetic of amino acid delivery to the organism has an influence on the efficiency of protein utilization. In particular, caseins, slowly digested milk proteins, promote a better protein balance than rapidly digested milk soluble proteins in young subjects (Boirie et al., 1997). In addition, changing protein feeding pattern (80% of daily protein consumed at noon vs 25%) significantly affect protein balance (Arnal et al., 2000). In young healthy individuals, the best protein efficiency is obtained by spreading protein absorption over time (casein, and/or 4 isoproteic meal per day). On the contrary, in older individuals, due to alteration in the sensitivity of protein metabolism to feeding, it is better to use rapidly digested proteins (Dangin et al., 2003), and / or to have a protein-rich meal once a day (Arnal et al., 1999).

Another physiological situation that was not studied in this regard is obesity. Obesity incidence is rapidly increasing around the world. When body mass index (weight / height2) becomes too high (>30), it is often suggested to restrict energy intake. However, severe energy restriction leads to fat mass loss, but also to lean body mass loss, which should be prevented. Our aim is to test whether for an adequate amount of total protein, it is possible to preserve lean body mass by using either casein, or milk soluble proteins, or by changing protein feeding pattern.

Inclusion Criteria:

• BMI>30
• sedentary
• normal TSH

Exclusion Criteria:

• any serious health problem