From Ergo Log
If you lose weight on a diet containing relatively high levels of protein, you lose weight quicker and better: you lose less muscle and more fat. Ok, we all knew this already – old news. What may be new is that on a weight loss protein-rich diet you also feel better. Researchers at Tufts University discovered that losing weight on a diet containing a normal amount of protein leads to feelings of depression, whereas a high-protein weight-loss diet works in the opposite way.
The researchers did an experiment with 42 overweight adults aged 20-42. The researchers put the test subjects on a diet for six months, during which time the subjects got 10 or 30 percent less energy than they burned. One half was put on a diet which the researchers, a little confusingly, refer to as high glycemic. It was actually a standard weight-loss diet containing 15 percent protein. The other half was put on a diet that consisted of 30 percent protein. The researchers called this diet ‘low glycemic’.
Before and after the six-month period the researchers asked their test subjects how they were feeling. For this they used the Profile of Mood States questionnaire [POMS] – a standard list of questions that psychologists use to detect aberrant states of mind. The POMS questionnaire contains questions on tension, depression, anger, energy and confusion. The researchers noticed that there was a statistically significant difference between the scores for depression for the two different groups.
The black circles represent the 15-percent-protein group. This group’s score for depression goes up. For the 30-percent-protein group [the white circles] the score actually goes down a little.
“Given that adverse changes in mood may negatively impact a long-term commitment to healthy eating habits and weight control, our findings suggest a potentially important psychological benefit of consuming higher protein diets for weight loss”, the researchers conclude. “Further studies in this area are warranted.”
Physiol Behav. 2009 Sep 7; 98(3): 374-9.