The use of high-protein diets have intermittently come under immense criticisms from a lot of nutrition experts. Despite these criticisms, the use of these diets have continued to receive a lot of increased interest from weight loss seekers.
High-protein diets are essentially diets in which about 20% or more of the total daily calorie consumption comes from proteins. These diets attempt to reduce the amount of consumed carbohydrate while making increased protein consumption the mainstay of the diet.
However, nutrition experts are of the opinion that although eating a high-protein diet may actually reduce food intake due to the fact that they make people become quickly satiated and for longer while also increasing the thermic effect of food temporarily, the long-term health risks such as kidney problems, bone mineral loss, and other risk factor outweigh the benefits.
Notwithstanding the above, especially the issue of high-protein diets not being really sustainable for long, with some adjustments, these diets can however become very effective and sustainable diet plans. So, how exactly does a high-protein diet really affect weight loss?
Proteins are fundamentally made from amino acids and for the most part are not stored in the body because the resultant amino acids are metabolized or split apart by enzymes within hours. While the resulting nitrogen is excreted by the kidney in urine, the remaining amino acids are either converted into glucose to be used for energy or stored as glycogen. However, protein is generally regarded as an inefficient source of energy fuel partly due to the fact that it is the hardest and slowest to be metabolized of the three macronutrients.
Naturally, the muscle cells and brain are designed to run exclusively on glucose which is a faster burning energy as it’s quite rapidly processed from carbohydrate foods. The brain is also known to consume about 80% of our calories while we are at rest.
High-protein low-carbohydrate diets however result in a significant reduction in available blood glucose causing decreased energy. The low glucose level triggers the release of a hormone called glucagon which causes two different but interrelated processes (glycogenolysis and lipolysis) to take place.
In response to the low blood sugar level, the pancreas secretes glucagon which triggers the process of glycogenolysis through signaling cells in the liver and muscle to release glycogen which is subsequently converted back into glucose for use by the body. Additionally, glucagon triggers the process of lipolysis – the release of fat from fat cells for use as energy fuel.
Glucagon therefore has the opposite effect of insulin on blood sugar level. While insulin is known as a store-and-save hormone that removes glucose from the bloodstream for storage as glycogen in liver and muscle cells and as fat in fat cells (adipose tissues), glucagon on the other hand does just the opposite as it causes the release and conversion of stored glycogen back into glucose and also releases stored body fat from fat cells for energy production.
The process of using stored glycogen causes a drastic weight loss occasioned by a major loss of water from body cells. This loss of water is drastic because a stored glycogen molecule is comprised of about 75% water and 25% glucose. Additional body water loss is occasioned by the increased need to flush out nitrogenous wastes resulting from protein metabolism. The combination of both of these processes result in a lot of body water loss.
However, when glycogen stores become significantly depleted, the body is forced to further increase the rate of lipolysis (fat burning) to meet its energy demands. The increased lipolysis leads to a condition known as ketosis – whereby there is an increased accumulation of ketone bodies in the bloodstream due to the increased metabolism (burning) of stored body fat for energy. Forcing the body to get to the point of moving into the secondary stage of lipolysis (ketosis) is actually the ultimate aim of a high-protein low-carbohydrate diet.
One of the unfortunate side effects of ketosis is the increased buildup of ketone bodies in the bloodstream. Ketones are the by-products of the break down of fat into fatty acids. Although under normal circumstances they are quickly oxidized to water and carbon dioxide, however the production of ketones in a state of ketosis is much higher than the rate at which they are capable of being oxidized by body tissues. This consequently leads to acidosis – a state of abnormal increase in blood acidity. In order to effectively rid itself of the accumulated ketones in the blood, the body subsequently increases its urinary output leading to further body water loss.
Therefore, the use of a high-protein low-carbohydrate diet results in a significant loss of body water through at least three mechanisms which include the: release and conversion of glycogen into glucose; flushing out of nitrogenous wastes resulting from protein metabolism; and flushing out of ketones from the body.
Besides the above body water loss effects which normally occur during the first phase of about two weeks of using a high-protein low-carbohydrate diet, there are equally other weight loss effects which can be caused by increased protein intake. These diets have the ability to cause early satiety thereby making people eat less while staying fuller for much longer time. Also, the high thermic effect of protein-containing foods plays another significant part.
The thermic effect of foods refers to the amount of daily calories that is utilized in eating, digesting and absorbing food. This energy accounts for about 10% of all our daily calorie expenditure. However, about 20-30% of the calories derived from protein-containing foods are used up in metabolizing them compared to the 6-8% and 2-3% used for carbohydrates and fats respectively. Therefore proteins do not just make you feel fuller but it is equally harder to metabolize and therefore burns more calories.
Nevertheless, the real weight loss effect of using a high-protein low-carbohydrate diet comes from the effect of the induced state of ketosis. The increased fat burning experienced in this condition causes one of the most significant and rapid weight loss effect possible.
Most high-protein low-carbohydrate diets start with very low amounts of carbohydrate intake aimed primarily at inducing the state of ketosis during the initial phase of the diet. However, subsequent phases which can be up to three or more, allows the dieter to gradually start increasing the amount of consumed carbohydrate until he or she achieves his or her weight loss goal and neither loses nor adds weight.
The major drawback of most low-carbohydrate diets has always been the reported issue of them not being sustainable due to the reduced energy levels a lot of people experience. This can however be overcome by following through with the prescribed phases or stages of the diet and modifying the final phases to achieve and maintain your desired body weight.