What are fast diets and what are they for?
By fast weight loss diets we mean all dietary regimes aimed at the rapid reduction of fat and body weight.
The target of any weight loss diet is the triglycerides enclosed in the cells of the subcutaneous adipose tissue.
Is body fat all the same?
Body fat, in addition to not being all the same, is distributed in various districts and differs in many types.
In addition to under the skin, other deposits are located inside the muscles, around them and in the abdominal cavity.
The one defined as "essential" (3-4 times greater in women than in men) is of vital importance and should not be affected by weight loss.
Essential or primary fat: it must not be affected by fast weight loss diets
Some types of “primary fat: are: brown adipose tissue (thermogenic), central nervous structures and nerves, bone marrow, organ structures, women's mammary glands, etc.
Significant reduction in essential fat (severe clinical symptoms and signs) is an indicator of continued malnutrition.
Body fat percentages: let's be clear
In the evaluation of the nutritional status it is necessary that the reading of the results referred to the plicometry or to the BIA (bioimpedance analysis) clearly distinguishes the values of total fat and adipose deposits.
To be clear, a male result of FAT 6% can have two meanings:
- 6% fat deposits, to which 3% primary fat must be added for a total of 9%
- Total fat 6%, from which 3% of the essential fat must be subtracted to obtain the value of the deposits equal to 3%.
WARNING! Both plicometry and BIA are indirect evaluation methods and to guarantee their accuracy it is necessary that specific calculation algorithms be used for a certain population group (men, women, athletes, clinicians, normals, etc.).
Essential Features of Weight Loss Diets
Slimming diets, to be defined BALANCED, must first of all possess some requisites:
- Be well balanced and provide all essential nutrients, with a caloric reduction of no more than 30% (no more than 500-800 kcal compared to necessary).
- Under no circumstances should the weight loss diet fall below the basal metabolic rate or 1.200 kcal for an adult, physically active, in good health.
- During a weight loss diet you should not lose more than 0,5 - 1,0 kg per week
- Include foods:
- Acceptable from a socio-cultural point of view (see religious impositions, philosophical currents, etc.)
- Easy to manage
- Simple to work and cook
- Economically sustainable
- Ecologically sustainable.
What distinguishes fast weight loss diets from normal ones?
Fast weight loss diets are fundamentally characterized by the "greater speed with which they drop the needle of the balance".
We could have simply said "the top weight loss rate", but that would have been a partial inaccuracy.
In fact, fast weight loss diets have the questionable property of reducing fat mass (FM) as well as fat-free mass (FFM).
The fat-free mass compartment consists of all tissues and liquids that do not contain relevant percentages of triglycerides.
The portion of FFM that negatively undergoes the action of fast weight loss diets consists of:
- Hepatic glycogen and, in athletes, also muscle glycogen (with consequent decrease in the water linked to it), due to the imbalance between the intake of carbohydrates in the diet and consumption with any motor activity
- Blood plasma and interstitial fluids, due to dehydration
- Striated skeletal muscle fibers, regarding the catabolism triggered by insufficient nutritional intake and possibly aggravated by motor activity.
This occurs especially in the very early stages of fast weight loss diets, when it is possible to witness the loss of 2-3 kg in just one week.
However, a decrease in body volumes is almost always evident NOT synchronized with the reduction of the most significant adipose panniculi (measurable by measuring the circumferences in centimeters of the waist, hips and thighs, etc.).
In the most extreme cases, it is even detectable an excessive decrease in muscle volumes (generally, measured with the circumference of the arms) compared to the reduction in fatty tissue.
On the contrary, the progress of a balanced weight loss diet is, even if less evident, related to the emptying of adipose tissue.
Why is it wrong to choose fast weight loss diets?
As we specified in the previous paragraph, balanced weight loss diets must ensure a weight loss rate of up to 4 kg per month.
This is because exceeding this threshold increases the risk of
- Malnutrition: due to a lack of one or more nutrients, essential or otherwise necessary for general health
- Early abandonment: due to excessive psycho-physical effort (frequent in sportsmen).
Obviously, for the weight loss of healthy people, the slower the weight loss and the lower the risks we talked about.
However, the psychological aspect must also be taken into account. A too slow weight loss is certainly not very motivating but, in the end, it is a subjective variable.
What are the risks of following fast weight loss diets?
The risks of fast weight loss diets are many and sometimes slightly different depending on the strategy adopted.
Among the most frequent we mention:
- Weakness, exhaustion, asthenia, reduction of psycho-physical functions
- Worsening of sports performance (all, especially of long duration)
- Ketogenesis and tendency to metabolic ketoacidosis: due to the lack of carbohydrates which determines a decompensated energy metabolism
- Tendency to dehydration
- Tendency to constipation
- Alteration of the composition of the intestinal bacterial flora
- Reduced urination, with dark and sometimes strong-smelling urine
- In predisposed subjects, increased chances of renal lithiasis; this occurs due to: dehydration and the change in urinary pH.
- In predisposed subjects, increased chances of biliary lithiasis; this can happen for: the lack of alimentary fats that do not allow the regular emptying of the gallbladder, for dehydration and / or for the imbalance of the bile.
- Tendency to:
- Low blood pressure (hypotension)
- Low blood sugar (hypoglycemia)
- Anemia (reduction of related factors, such as corpuscular volume, sideremia, ferritinaemia, transferrinemia, plasma vitamin B12 and folic acid, etc.)
- Muscle catabolism.
- Muscle cramps.
- General deterioration, also visible by many clinical signs affecting the skin, mucous membranes, hair, nails, etc.
- For more restrictive diets, in the very long term, the reduction of the basal metabolism can occur.
Most popular types of fast weight loss diets
Mediterranean-like diets with insufficient energy intake
It is defined as such if to a sedentary subject it offers fewer calories than the basal metabolism or if it assigns less than 70-90% of normal energy to a sportsman (varies depending on the case).
It maintains a distribution similar to that of a balanced diet but, due to the inadequate overall nutritional intake, it deteriorates the organism more or less quickly.
They emphasize reducing carbohydrates for the benefit of protein and fat, generally without taking into account the total calorie content of the diet.
Such a dietary approach has undoubted slimming effects, as it promotes the mobilization of fats for energy purposes and reduces appetite. See: Metabolic Diet and Atkins Diet.
Harmful effects: increase plasma levels of uric acid (gout), alter electrolyte balance and promote dehydration of the body, increase urinary calcium loss (could increase the risk of osteoporosis), increase plasma lipids (hypercholesterolemia and greater risk for cardiovascular disease ); they deplete the body's glycogen stores, significantly decreasing the ability to train and compete.
The dietary approach is similar to the previous one, but less extreme; many reduce both the concentration of carbohydrates and lipids.
They are proposed as diets of the last "chance" to prepare quickly for the costume test. Positive and negative effects are similar to those of ketogenic diets.
Diets based on fasting, total and intermittent or only partial
Strongly low-calorie (from 0 to less than 500 kcal every 12 hours), most (but not all) are based on the administration of vegetable-based meals, smoothies and slimming herbal teas.
They ensure rapid weight loss, but significantly slow down the basal metabolism (especially with fasts exceeding 48 hours) and, in the medium-long term, they can only have one effect: increase the tendency to gain weight of the person who has undertaken them (good part of the weight lost goes to the detriment of muscle mass, while the percentage of fat remains substantially unchanged).
Single issue diets
Their low calorie content promotes weight loss, negativising the energy intake. They appeal to people with little knowledge of food since, being easy to follow, they have a good psychological approach to those who follow them.
This particular type of weight loss diets, due to the extreme restrictiveness, ends up generating deficiencies in nutritional principles. After a few weeks the diet becomes boring and the organism itself, depleted of some nutrients, asks for the suspension of the diet (weakness, mental fatigue, gastrointestinal problems).
Is there a fast weight loss diet that is ideal for everyone?
No, as the very definition of "fast weight loss diet" suggests that it is an inadequate system.
On the contrary, referring to the less extreme weight loss strategies, we could answer yes; the ideal weight loss diet exists and it is all in all easy to adopt.
It consists in making various but small changes to one's lifestyle, reconciling a little physical activity with the gradual elimination of those habits that contribute to an incorrect diet.
A fundamental prerequisite for achieving this goal is correct information.
This site is happy to offer you numerous articles to help you lose weight without resorting to the slimming diets just described and of questionable health.
Among the more than 2.000 articles, we recommend that you first read the following:
- Calculate your ideal weight
- Food advice
- Unnecessary calories
- Calculation of calories
- What sport to lose weight
- Example 2000 calorie diet (and other free weight loss diets)