Adaptation of eating behaviour to reduced dietary protein intake in rats: influence of the amount of protein and amino acid composition in the diet.

Reducing meat consumption is encouraged to improve diet environmental sustainability. It results in reducing protein intake, and this can have consequences on eating behaviour. To better characterise these consequences, six-week-old male Wistar rats were divided into 5 groups receiving diets differing by their protein source and amount. Two groups received a casein (C) diet, containing 20% (C20) or 6% (C6) protein, a casein density known to induce a hyperphagic response in rats. Three groups received a dehydrated bovine protein (DBP) diet, containing 6% (B6), 10% (B10), or 20% (B20) protein. C20 and B20 rats had also free access to 40% protein pellets (casein for C20 and DBP for B20), but choose to maintain their protein intake close to 20%. C20 and B20 rats showed similar growth and food consumption throughout the 12-week experiment. B6 rats showed reduced growth (-26%) and lean body mass despite similar food consumption to B20. C6 and B10 rats increased their food intake (C6 by +20% relative to C20; B10 by +30% relative to B20) and showed similar growth to C20 and B20 rats. Comparison of amino acid intakes suggests that the amplitude of food overconsumption allowed C6 and B10 rats to achieve a threshold intake of specific essential amino acids. C6 and B10 rats had more visceral adiposity than C20 and B20 rats, but similar lean body mass. Our results characterize the hyperphagic response to moderate meat protein reduction, showing that it increases adiposity, then providing some insights into the obesogenic risk potentially associated with reduced meat consumption.