OPTIMAL PROTEIN INTAKE WHILE DIETING: PART 2
- The optimal protein intake while dieting should be roughly 1.5 grams per pound of bodyweight
- When not dieting, greater protein doses greater than 1 gram per pound of body weight don’t increase muscle growth.
- Overfeeding studies with protein have not found additional gains in body fat
- High protein diets result in greater appetite suppression
YOU NEED MORE PROTEIN WHILE DIETING
Why do you need more protein while dieting? Rates of muscle protein synthesis drop by 27% after only five days of moderate energy restriction.(1) You need more protein to compensate for the reduction in muscle protein synthesis. As your calories and body fat are reduced, your body goes into a conservation mode and uses energy from the most readily available tissues.
In this case, it’s muscle!! Muscle provides 13 calories/per kg/day, whereas fat provides 4.5 calories/per kg/day.(2) This makes muscle an easy target for the body to pull calories from when in a deficit. Most weight loss clinics will often include essential amino acid supplements while following a calorie-restricted diet to maintain protein synthesis while being very low in calories.
Most research studies classify high-protein diets based on grams per kg of body weight (g/kg/bw). The International Society of Sports Nutrition defines “high protein” as anything over 2.2 g/kg/bw per day or 1 gram per pound of body weight. What’s so important about the 2.2 g/kg/bw mark for protein?
Protein and Lean Muscle Mass
In a well-documented study by Tarnopolsky et al., American football players and rugby players performing resistance exercises were assigned to a low protein (0.86 g/kg/day), moderate protein (1.40 g/kg per day), and high protein (2.40 g/kg/day); the lowest protein diet impaired protein synthesis, however, 2.4 g/kg/day did not result in greater increases in protein synthesis.
Leucine oxidation or breakdown increased in the high protein group, indicating the protein was being used as an energy source rather than stored in muscle protein.(3) This study was conducted back in the early 90s using nitrogen balance, but it was a critical step in showing that trained resistance men need more protein.
Keep in mind, these were diets at maintenance levels with adequate calories, but it helps set the optimal protein intake while dieting and to build muscle should be at the 1.4 to 1.7 g/kg/bw will at maintenance levels.
Optimal Protein Intake and the RDA
Protein intake needs to be increased when dieting to retain lean muscle loss with restricted calories. When protein intake exceeds 2.2 g/kg/bw, there are numerous beneficial effects on body composition. Researchers assigned subjects to a 30% caloric restriction while increasing their energy expenditure by 10% but varied the protein content. Subjects either received 0.8 g/kg/be (recommended dietary allowance; RDA), 1.6 g/kg/bw (2×-RDA), and 2.4 (3×-RDA) for 31 days.
Those assigned the higher protein (i.e., 2-3x-RDA) lost less muscle and more fat than the low protein group. In a similar study, athletes were assigned to a 40% reduction in calories, with groups either receiving a low (1.0 g/kg/day) or high protein (2.3 g/kg/day) diet.
The high protein group lost less muscle mass and similar amounts of body fat as the low protein group. Interestingly, the high protein group had more favorable changes in testosterone and growth hormone responses.(4) It’s well established that overfeeding with diets high in carbohydrates and fat results in gains in fat mass.(5) Even when excess calories are provided, greater protein intake does not contribute to fat gains.(6)