There are several major types of diets interspersed with a multitude of subtypes, which creates a maze of conflicting principles that can be difficult for the general public and professionals.
The increase in confusion is the continued spread of fad diets through a wide range of media, replete with unfounded practices.
Therefore, it is important to examine the scientific evidence in a systematic manner in order to develop recommendations to guide health professionals (coaches, dieticians and sports nutritionists), athletes and the general public with regard to everything the above.
This was precisely the purpose of a recent review of the International Society of Sports Nutrition published this year 2017, which has given its position on the effects of various diets on body composition.
Meaning of “diet”, types and importance of body composition
A general definition of “diet” is the sum of energy and nutrients obtained from foods and beverages consumed regularly by individuals.
In this review , the International Society of Sports Nutrition has evaluated various dietary archetypes : diets low and very low energy, low – fat diets, low carb diets / ketogenic , high protein diets and intermittent fasting .
In turn, and simply as information, it is important to know that body composition is inextricably linked to the fundamental parameters of health, in that, for example, a greater proportion of lean mass reduces the risk of developing metabolic syndrome, bone loss and the multiple complications associated with sarcopenia (degenerative loss of muscle mass and strength due to aging or sedentary lifestyle).
That said, these are the conclusions and recommendations of the International Society of Sports Nutrition on the effects of various diets on body composition.
Multitude of diets: Let’s base ourselves on science
There is a great multitude of diets. In addition, there are numerous subtypes that fall under the main archetypes of the diet. Practitioners, clinicians and researchers need to maintain an understanding of the claims versus the evidence underlying each archetype to adequately guide science-based practical and educational objectives with clients, patients and the public.
Methods of evaluation of body composition
All methods of evaluating body composition have strengths and limitations . Therefore, the selection of the method must weigh the practicality and the coherence with the prohibitive potential of costs, invasiveness, availability, reproducibility and technical skills requirements.
Ultimately, the needs of the client, patient or research questions must be matched with the chosen method, with individualization and environmental considerations being absolutely essential.
Diets to lose fat mass: caloric deficit
Diets focused primarily on the loss of fat mass (and weight loss beyond the initial reductions in body water) operate under the fundamental mechanism of a sustained caloric deficit .
This net hypocaloric equilibrium can be imposed linearly (daily), or not linearlythroughout the week. The higher the reference fat mass level, the more aggressively the caloric deficit can be imposed.
As subjects become thinner, the slower rates of weight loss can better preserve lean mass (muscles, bones and internal organs).
Diets to gain muscle mass: calorie surplus
Although lean mass gains have been reported in the literature during hypocaloric conditions, diets focused primarily on lean mass gain are likely to be optimized through a sustained caloric surplus to facilitate anabolic processes and support growing demands. of training.
The composition and magnitude of the surplus, the inclusion of an exercise program , as well as the training status of the subjects can influence the nature of the gains.
The larger caloric surpluses are more appropriate for untrained subjects who are prepared for more dramatic progress in gaining lean mass and for those with a high level of thermogenic activity not associated with physical exercise ( NEATconcept = non-exercise activity thermogenesis ).
On the other hand, smaller caloric surpluses are appropriate for more advanced subjects in training who may be at a higher risk for undue gain of fat mass during aggressive hypercaloric conditions.
In turn, it should be noted that not all subjects will conform to this general framework . Some rookies may require smaller surpluses, while some advanced subjects will require higher surpluses to boost muscle gains.
It is the job of the practitioner to adapt the programs to the inevitable variability of the individual response.
Low-fat diets vs low-carbohydrate (ketogenic) diets
A wide range of dietary approaches (low-fat, low-carbohydrate / ketogenic diets, and all points between them) can be equally effective in improving body composition , and this allows flexibility with the design of the program.
To date, no controlled isocaloric diet comparison where the protein matchesbetween the groups has reported a clinically significant fat loss or a thermal advantage for the low carbohydrate or ketogenic diet . The collective evidence in this regard invalidates the carbohydrate-insulin hypothesis of obesity.
However, ketogenic diets have shown an appetite suppression potentialexemplified by the spontaneous reduction of caloric intake in subjects with ketogenic diets without intentional caloric restriction.
If we talk about sports performance , this is a separate goal with variable demands on the availability of carbohydrates depending on the nature of the sport. The restriction of carbohydrates can have an ergolytic potential(detrimental to performance), particularly for endurance sports.
In terms of strength and potency , the effects of carbohydrate restriction on them justify additional research .
High protein diets
Increasing dietary protein to levels significantly beyond current recommendations for athletic populations can improve body composition, with the recommendation for these populations being between 1.4 and 2 g / kg body weight .
Higher protein intakes of between 2.3 and 3.1 g / kg of fat-free mass may be required to maximize muscle retention in strength-trained subjects who have a large amount of lean mass in hypocaloric conditions.
In turn, emerging research on very high protein intakes (more than 3 gr / kg)have shown that the known thermal, satiating and preservative effects of lean mass of dietary proteins could be amplified in subjects trained in strength.
It is possible that said protein calorie surpluses result in a eucalyptus balancethrough satiety- mediated decreases in total calories, increased heat dissipation and / or lean mass gain with loss of concurrent fat mass.
Intermittent caloric restriction
The intermittent calorie restriction combined with strength training is an emerging area of research that has so far shown mixed results.
However, taken together, the body of research on intermittent caloric restriction has not indicated any significant advantage over daily caloric restriction to improve body composition.
Therefore, the programming of the linear versus non-linear caloric deficitshould be determined by individual preference, tolerance and athletic goals.
The strength training and the appropriate amount of protein , plus an adequate rate of weight loss, should be the primary approach to achieving the objective of the retention (or gain) of lean body mass during the loss of fat mass.
The adaptive thermogenesis is a term used to describe the gray area where losses in metabolic tissue can not simply explain the reduced energy expenditure.
The long-term success of the diet depends on the efficacy with which the attenuating factors of the homeostatic unit are suppressed or eluded.
The hypocaloric conditions for fat loss have resulted in said adaptive thermogenesis, a greater than expected decrease in energy expenditure (10-15% below the predicted drop in total daily energy expenditure after calculating lean mass and loss of fat mass).
However, most of the existing research demonstrating adaptive thermogenesis has involved diets that combine aggressive caloric restriction with low protein intakes and the absence of strength training , essentially creating, therefore, a perfect storm for deceleration of metabolism.
Research that has carefully included strength training and adequate protein has avoided the problem of adaptive thermogenesis and loss of lean mass, despite very low calorie intakes.
Lack of research in different populations and doubts
There is a shortage of research in women and older adults , as well as a wide range of unexplored permutations of feeding frequency and distribution of macronutrients in various energy balances combined with training.
Behavior modification and lifestyle strategies are still poorly researched areas of weight management.
An ideal scenario (although certainly not always feasible) is a multidisciplinary team approach for the person, that is, dietitian, personal trainer , psychologist, and doctor.
This makes the most efficient use of experience in covering the various facets of lifestyle modification, and when necessary, medical intervention.
In summary, research on the effects of diet on body composition has a lot of gray areas and mature paths for research (although it is true that many previously unknown things are already known).
While a certain amount of our current knowledge will remain static, scientists, both in the laboratory and in the field, must remain vigilant and open to the modification and falsification of models and beliefs as the progress of the investigation continues.