The Role of Dietary Protein in Weight Loss
Why is protein regarded as the king of macronutrients? You might already be aware of its importance when it comes to building muscle and regulating bodily functions, but did you know it can also help you lose fat more efficiently?
For those seeking to lose weight, protein intake becomes increasingly more significant as energy intake and bodyweight decrease.
There are many ways in which dietary protein can assist in fat loss. It does so by prolonging satiety under hypocaloric conditions, by promoting an increase in energy expenditure through food thermogenesis, and by maintaining one’s metabolism high despite a decrease in bodyweight (due to a preservation of lean body mass).
In this article I will explore each of its relevant role in optimizing body composition during a diet phase, and how you can use simple nutritional strategies that will get you the best results when trying to lose body fat.
Compared to fats and carbohydrates, protein has been shown to induce greater satiety following a meal. This prolonged fullness derived from a high-protein meal can then result in a lower daily caloric intake, which over time can contribute to weight loss.
Protein has the highest satiety effect of the three macronutrients, with fats having the lowest effect and carbohydrates being somewhere in the middle. This helps explain why energy-dense snacks like chocolate and nuts won’t keep you full for long, compared to less energy dense, higher-protein foods such as yogurt.
Next time you’re craving a snack in between meals, opt for something protein-heavy and pay attention to how that affects your appetite for the following meals.
Thermic Effect of Food
The thermic effect of food refers to the amount of energy utilized by the body in the breakdown and processing of macronutrients.
Not surprisingly, protein has a greater TEF compared to carbohydrates and fats, sitting at about 20-30% while carbohydrates use up 6% of total calories and fats about 2-3%. That means you would spend about 30% of the calories ingested from protein sources in simply breaking it down and processing the macronutrient. This might not mean much, but in the big picture and over a prolonged period of time, it could translate into a significant difference for some individuals.
For example, if you ingest 100 calories of fats or carbs, you’d burn about 3 and 6 calories respectively. Similarly, if you consumed 100 calories worth of protein, you’d burn about 25 calories by simply processing it. By replacing carbs and fats with protein in more extreme high-protein diets, you can see how these numbers can quickly rack up and impact your total daily energy expenditure.
Due to its effect on energy expenditure over a prolonged period of time, it makes sense why a diet higher in protein and lower in the other two macronutrients would generate the best results.
Weight Loss vs. Fat Loss
Studies have shown that under hypocaloric conditions, a high-protein diet yielded similar results to a low protein diet when both energy intakes were matched. However, only a high-protein diet resulted in a greater loss of fat mass and a greater retention of lean or fat-free mass.
In one study, two groups were matched for calories and fed either a low-protein (with 15% of total daily calories coming from protein) or a high-protein diet (30% of total caloric intake). While the low-protein group lost more overall weight as a result (about 11.4 kg+/-3.8kg, with 37.5% of it being LBM), the high-protein group was able to spare as much as half of the lean body mass (8.4kg +/- 4.5kg total weight loss with 17.5% LBM).
Why does this matter?
The ultimate goal of weight loss should be to preserve as much fat-free mass as possible. Lean mass contributes to an elevated basal metabolic rate (in other words, an increase in metabolic activity). A higher BMR will help keep the lost weight off for longer, as the body will continue to burn more calories even at rest. For that reason, high-protein diets are more sustainable in the long-term (due to its satiety effects and its impact on metabolic activity), and thus have a greater impact on the prevention of obesity.
So, what exactly is lean body mass? Simply put, it is the amount of mass you carry on your body that does not contain any fat. This includes muscle mass (which contributes to the greatest changes in LBM), water, bones, the weight of your organs, and anything else in between that isn’t adipose tissue.
Aside from the strength and aesthetic benefits of having higher lean muscle mass, there are also health benefits associated with it. Your immune system can be heavily affected by a loss of LBM, therefore it is important to retain as much LBM as possible during weight loss. Lean body mass will also assist in protecting your bones from becoming weaker over time, which reduces the chances of osteoporosis at an older age.
How much protein is enough?
Okay, you get it. Protein intake matters, and even more so during a fat loss phase. But how much of it is enough to preserve LBM?
The recommended daily allowance of protein is around 0.8 g per kilogram of body weight. For individuals who exercise, that number is already on the low side. Couple that with a caloric deficit for an extended amount of time and you’re setting yourself up for big losses (and I don’t mean the good kind).
Although individual recommendations vary, studies have shown that the optimal protein intake for someone in a weight loss phase ranges from 1.6 g/kg and upwards to as high as 2.8g/kg.
For myself and my clients, I personally recommend no less than 1g/lb of bodyweight (2.2g/kg).
When you restrict your body of calories, protein breakdown increases as more protein is then used up as energy. Similarly, the more fat you lose and the leaner you are, the more protein is used up by the body and therefore your protein requirements also increase. With that in mind, I believe it is better to err on the extra side of protein intake, which will certainly help spare lean body mass while in a caloric deficit. Contrary to popular belief, a diet high in protein will not cause renal dysfunction in individuals without any pre-existing health conditions.
While overall energy balance is the sole determinant of weight loss, a diet that is high in protein will generate better results in terms of body composition. The goal of any weight loss diet should be to preserve as much fat-free mass as possible, while minimizing the risk of weight gain following its completion. High-protein diets do so by increasing satiety, maintaining a high basal metabolic rate by preserving lean body mass, and by inducing greater food thermogenesis.
If you have any questions or would like to know more about implementing sound nutritional strategies into your routine, shoot me an email at firstname.lastname@example.org.
Laflamme, D. P., & Hannah, S. S. (2005). Increased Dietary Protein Promotes Fat Loss and Reduces Loss of Lean Body Mass During Weight Loss in Cats. The International Journal of Applied Research in Veterinary Medicine.
Leidy, H. J., & Clifton, P. M. (2015). The Role of Protein in Weight Loss and Maintenance. American Journal of Clinical Nutrition. doi:10.3945/ajcn.114.084038
Noakes, M. (2008). The Role of Protein in Weight Management. Asia Pacific Journal of Clinical Nutrition.
Paddon-Jones, D., & Westman, E. (2008). Protein, Weight Management, and Satiety. American Journal of Clinical Nutrition.
Phillips, S. M. (2014). A Brief Review of Higher Dietary Protein Diets in Weight Loss: A Focus on Athletes. Sports Medicine, 44(S2), 149-153. doi:10.1007/s40279-014-0254-y
Westerterp-Plantenga, M. S., Lemmens, S. G., & Westerterp, K. R. (2012). Dietary protein – its role in satiety, energetics, weight loss and health. British Journal of Nutrition, 108(S2). doi:10.1017/s0007114512002589