Tag Archives: mediterranean diet

Potassium intake, blood pressure and hypertension

Potassium intake and blood pressure

High dietary potassium (K+) intakes and blood pressure are inversely related: animal studies, observational epidemiological studies, clinical trials, and meta-analyses of these trials support this.
Furthermore, the prevalence of hypertension tends to be lower in populations with high K+ intakes than in those with low intakes.
Finally, an increase in potassium intake (2.5-3.9 g/d) reduces blood pressure in normotensive and hypertensive, and to a greater extent in blacks than in whites.

Dash Diet and potassium intake

Controlled feeding studies (“The Dietary Approaches to Stop Hypertension (DASH) Study” and “OmniHeart Trial”) have highlighted the role of a good potassium intake, along with other minerals and fiber, in blood pressure reduction.
These studies have shown that a dietary pattern rich in fruits, vegetables, and low-fat dairy products, with whole grains, poultry, fish and nuts but poor in fats, red meat, sweets, and sugar-containing beverages reduces blood pressure.
These dietary patterns are rich in foods high in K+, as well as magnesium, calcium and fiber, but poor in total fat, saturated fat and cholesterol.
The best result on lowering blood pressure are with black participants than white participants.

Potassium, sodium and blood pressure

The effects of potassium on blood pressure depend on the concurrent intake of sodium and vice versa:

  • an increased intake of K+ has:

a greater blood pressure-lowering effect when sodium intake is high;

a lesser blood pressure-lowering effect when sodium intake is low;

  • on the other hand, the blood pressure reduction from a lowered sodium intake is greatest when potassium intake is low.

An high K+ intake also increases urinary excretion of sodium, the so-called natriuretic effect.
In the generally healthy population with normal kidney function the recommended potassium intake level is 3.1 g/day. But, in the presence of impaired urinary potassium excretion, a K+ intake less than 3.1 g/day (120 mmol/d) is appropriate, because of adverse cardiac effects (arrhythmias) from hyperkalemia, that is, blood potassium level higher than normal.

Mediterranean Diet and potassium intake

Potassium
Fig. 1 – Fruit, Vegetables, and Blood Pressure

As already pointed out, the best strategy to increase K+ intake is to consume legumes, and fruits and vegetables in season, i.e. foods high in  potassium, that is also accompanied by a variety of other nutrients. No supplements are needed.
Therefore, it is sufficient to follow a  Mediterranean dietary pattern, for:

  • meet the daily requirements of the mineral;
  • consume K+ intake in adequate amounts to ensure its blood pressure-lowering effect.

Potassium content in some foods

High content: >250 mg/100 g of product

  • Dried legumes (chickpeas, beans, lentils, peas and soybeans) and fresh beans;
  • garlic, chard, cauliflower, cabbage, Brussels sprouts, broccoli, artichokes, cardoons, fennel, mushrooms, potatoes, tomatoes, spinach, zucchini;
  • avocados, apricots, bananas, fresh and dried chestnuts, watermelon, kiwi, melon, hazelnuts;
  • sweet dried fruits (apricots, dates, figs, prunes, raisins etc..) and oily dried fruits (peanuts, almonds, walnuts, pine nuts, pistachios, etc.);
  • oat flour, whole wheat flour and spelt;
  • ketchup;
  • roasted coffee;
  • milk powder (also rich sodium);
  • yeast;
  • cocoa powder.

Medium content: 150-250 mg/100 g of product

  • asparagus, beets, carrots, chicory, green beans, fresh broad beans, endive, lettuce, peppers, fresh peas, tomatoes, leeks, radishes, celery, tomato and carrot juice, pumpkin;
  • pineapple, oranges, raspberries, blueberries, loquats, pears, peaches, grapefruit, grapes;
  • meat and fish products, both fresh and preserved (the latter, however, should be avoided because of their high sodium content).

Note: cooking methods tend to reduce the K+ content of the food.
To reduce potassium loss, avoid boiling in plenty of water, for more than an hour, vegetables cut into small pieces (this increases the “exchange area” with water).

References

Appel L.J., Brands M.W., Daniels S.R., Karanja N., Elmer P.J. and Sacks F.M. Dietary Approaches to Prevent and Treat Hypertension: A Scientific Statement From the American Heart Association. Hypertension 2006;47:296-08 [Abstract]

Cappuccio F.P. and MacGregor G.A. Does potassium supplementation lower blood pressure? A metaanalysis of published trials. J Hyperten 1991;9:465-73 [Abstract]

Geleijnse J.M., Witteman J.C., den Breeijen J.H., Hofman A., de Jong P., Pols H.A. and Grobbee D.E. Dietary electrolyte intake and blood pressure in older subjects: the Rotterdam Study. J Hyperten 1996;14:73741 [Abstract]

Mahan LK, Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Matlou S.M., Isles C.G. and Higgs A. Potassium supplementation in Blacks with mild to moderate essential hypertension. J Hyperten 1986;4:61-4  [Abstract]

Nutrient Data Home (USDA)

Pickering T.G. New Guidelines on Diet and Blood Pressure. Hypertension 2006;47:135-6 [Full text]

Rose G. Desirability of changing potassium intake in the community. In: Whelton P.K., Whelton A.K. and Walker W.G. eds. Potassium in cardiovascular and renal disease. Marcel Dekker, New York 1986;411-16

Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Tabelle di composizione degli alimenti; aggiornamento 2000. I.N.R.A.N.

Writing Group of the PREMIER Collaborative Research Group. Effects of Comprehensive Lifestyle Modification on Blood Pressure Control: Main Results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]

World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92. [Abstract]

Sodium: blood pressure, requirements, intake, sources

Sodium and blood pressure

A high sodium (Na+) intake (the main source is salt or sodium chloride, NaCl) contributes to blood pressure raise, and hypertension development.
Many epidemiologic studies, animal studies, migration studies, clinical trials, and meta-analyses of trials support this, with the final evidence from rigorously controlled, dose-response trials. Furthermore, in primitive society Na+intake is very low and people experience very low hypertension, and the blood pressure increase with age does not occur.
Probably, sodium intake effect sizes are to be underestimated!

Recommended daily intake of sodium

Sodium
Fig. 1 – Salt Pans of Trapani

Sodium’s physiologic requires are very low; in fact, the minimum recommended Na+ intake for maintain life is 250 mg/day (Note: iodized salt is an important source of dietary iodine in the United States and worldwide).
An Americans consumes the mineral in great excess of physiologic requires: despite the guidelines from the Departments of Agriculture and Health and Human Services, during the period from 2005 through 2006 the average salt intake in USA is of 10.4 g/day for the average man and 7.3 for the average woman, amount in excess regarding preceding years.
A study published on February 2010 on “The New England Journal of Medicine” have shown that “A population-wide reduction in dietary salt of 3 g per day (1200 mg of Na+ per day) is projected to reduce the annual number of new cases of coronary heart disease (CHD) by 60,000 to 120,000, stroke by 32,000 to 66,000, and myocardial infarction by 54,000 to 99,000 and to reduce the annual number of deaths from any cause by 44,000 to 92,000″ (Bibbins-Domingo et all., see References). These benefits are similar in magnitude to those from:

  • a 50% reduction in tobacco use;
  • a 5% reduction in body mass index among obese adults;
  • a reduction in cholesterol levels.

These benefits regard all adult group age, black and nonblack, male and female. The benefits for black are greater than nonblack, in both sex and all age group. It’s estimated an annual savings of $10 billion to 24 $ billion in health care costs.
Clinical trials have also documented that a reduced Na+ intake can lower blood pressure in the setting of antihypertensive medication, and can facilitate hypertension control.
But, in USA dietary salt intake is on the rise!
So, it is recommended, to prevent hypertension development, a reduction in its intake and, in view of the available food supply and the currently daily Na+ intake, a reasonable recommendation is an upper limit of 2.3 g/day (5.8 g/day of salt).
How achieves this level? It can be achieved:

  • cooking with as little salt as possible;
  • refraining from adding salt at the table;
  • avoiding highly salted, processed foods.

Dietary sources of sodium

Sodium
Fig. 2 – Salt Shaker

They include:

  • salt used at the table: up to 20% of the daily salt intake;
  • salt or sodium compounds added during preparation or processing foods: between 35 to 80% of the daily sodium intake comes from processed foods.
    Which foods are?
    Processed, smoked or cured meat and fish e.g. sliced salami, sausage, salt pork, tuna fish in oil etc.; meat extracts and sauce, salted snack, soy sauce, barbecue sauce, commercial salad dressing; prepackage frozen foods; canned soup, canned legumes; cheese etc.
    There are also many sodium-containing additives as disodium phosphate (e.g. in cereals, ice cream, cheese), monosodium glutamate (i.e. meat, soup, condiments), sodium alginate (e.g. in ice creams), sodium benzoate (e.g. in fruit juice), sodium hydroxide (e.g. in pretzels, cocoa product), sodium propionate (e.g. in bread), sodium sulfite (e.g. in dried fruit), sodium pectinate (e.g. syrups, ice creams, jam), sodium caseinate (e.g. ice creams and other frozen products) and sodium bicarbonate (e.g. baking powder, tomato soup, confections).
    So pay attention to ingredients!
  • Inherent sodium of foods. Generally low in fresh foods.

The blood pressure response to lower dietary Na+ intake is heterogeneous with individuals having greater or lesser degrees of blood pressure reduction. Usually the effect of reduction tend to be greater in blacks, middle-aged and older persons, and individuals with hypertension, diabetes or chronic kidney disease.
Furthermore genetic and dietary factors influence the response to sodium reduction.

How diet can modify response of blood pressure to sodium?

Some components of the diet may modify response of blood pressure to sodium.

  • A high dietary intake of calcium and potassium rich foods, such as fruit, vegetable, legumes (e.g. Mediterranean diet), and low-fat dairy products (e.g. DASH diet), may prevent or attenuate the rise in blood pressure for a given increase in sodium intake.
  • Some evidences, seen primarily in animal model, suggest that high dietary intake of sucrose may potentiate salt sensitivity of blood pressure.

Note: high Na+ intake can contribute to osteoporosis: they result in an increase in renal calcium excretion, particularly if daily calcium intakes are low.

References

Appel L.J., Brands M.W., Daniels S.R., Karanja N., Elmer P.J. and Sacks F.M. Dietary Approaches to Prevent and Treat Hypertension: A Scientific Statement From the American Heart Association. Hypertension 2006;47:296-08 [Abstract]

Bibbins-Domingo K., Chertow G.M., Coxson P.G., Moran A., Lightwood J.M., Pletcher M.J., and Goldman L. Projected effect of dietary salt reductions on future cardiovascular disease. N Engl J Med 2010;362:590-9 [Abstract]

Cappuccio FP. Overview and evaluation of national policies, dietary recommendtions and programmes around the world aiming at reducing salt intake in the population. World Health Organization. Reducing salt intake in populations: report of a WHO forum and technical meeting. WHO Geneva 2007;1-60 [PDF]

Chen J, Gu D., Jaquish C.E., Chen C., Rao D.C., Liu D., Hixson J.E., Lee Hamm L., Gu C.C., Whelton P.K. and He J. for the GenSalt Collaborative Research Group. Association Between Blood Pressure Responses to the Cold Pressor Test and Dietary Sodium Intervention in a Chinese Population. Arch Intern Med. 2008;168:1740-46 [Abstract]

Denton D., Weisinger R., Mundy N.I. et al. The effect of increased salt intake on blood pressure of chimpanzees. Nature Med 1995;10:1009-16 [Abstract]

Ford E.S., Ajani U.A., Croft J.B. et al. Explaining the decrease in U.S. deaths from coronary disease, 1980-2000. N Engl J Med 2007;356:2388-98 [Abstract]

Geleijnse J.M., Witteman J.C., den Breeijen J.H., Hofman A., de Jong P., Pols H.A. and Grobbee D.E. Dietary electrolyte intake and blood pressure in older subjects: the Rotterdam Study. J Hyperten 1996;14:73741 [Abstract]

Harlan W.R. and Harlan L.C. Blood pressure and calcium and magnesium intake. In: Laragh J.H., Brenner B.M., eds. Hypertension: pathophysiology, diagnosis and management. 2end ed. New York: Raven Press 1995;1143-54

Holmes E., Loo R.L., Stamler J., Bictash M., Yap I.K.S., Chan Q., Ebbels T., De Iorio M., Brown I.J., Veselkov K.A., Daviglus M.L., Kesteloot H., Ueshima H., Zhao L., Nicholson J.K. and Elliott P. Human metabolic phenotype diversity and its association with diet and blood pressure. Nature 2008;453:396-400 [First paragraph]

Mahan LK, Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Pickering T.G. New Guidelines on Diet and Blood Pressure. Hypertension 2006;47:135-6 [Full text]

Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Simpson F.O. Blood pressure and sodium intake. In: Laragh J.H., Brenner B.M. eds. Hypertension: pathophysiology, diagnosis and management. 2end ed. New York: Raven Press 1995;273-81

Strazzullo P., D’Elia L., Kandala N. and Cappuccio F.P. Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies. BMJ 2009;339:b4567 [Abstract]

Tzoulaki I., Brown I.J., Chan Q., Van Horn L., Ueshima H., Zhao L., Stamler J., Elliott P., for the International Collaborative Research Group on Macro-/Micronutrients and Blood Pressure. Relation of iron and red meat intake to blood pressure: cross sectional epidemiological study. BMJ 2008;337:a258 [Abstract]

Weinberger M.H. The effects of sodium on blood pressure in humans. In: Laragh JH, Brenner BM, eds. Hypertension: pathophysiology, diagnosis and management. 2end ed. New York: Raven Press 1995;2703-14

Writing Group of the PREMIER Collaborative Research Group. Effects of Comprehensive Lifestyle Modification on Blood Pressure Control: Main Results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]

World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92. [Abstract]

Alkaline diet and health benefits

Alkaline diet and bone health

The acid-ash hypothesis posits that protein and grain foods, with a low potassium intake, produce a diet acid load, net acid excretion, increased urine calcium, and release of calcium from the skeleton, leading to osteoporosis.” (Fenton et al., 2009).
Is it true?
Calcium, present in bones in form of carbonates and phosphates, represents a large reservoir of base in the body. In response to an acid load such as the high protein diets these salts are released into the circulation to bring about pH homeostasis. This calcium is lost in the urine and it has been estimated that the quantity lost with the such diet over time could be as high as almost 480 g over 20 years or almost half the skeletal mass of calcium!
Even these losses of calcium may be buffered by ingestion of foods that are alkali rich as fruit and vegetables, and on-line information promotes an alkaline diet for bone health as well as a number of books, a recent meta-analysis has shown that the causal association between osteoporotic bone disease and dietary acid load is not supported by evidence and there is no evidence that the alkaline diet is protective of bone health (but it is protective against the risk for kidney stones).

Note: it is possible that fruit and vegetables are beneficial to bone health through mechanisms other than via the acid-ash hypothesis.

And protein?
Excess dietary protein with high acid renal load may decrease bone density, if not buffered by ingestion of foods that are alkali rich, that is fruit and vegetables. However, an adequate protein intake is needed for the maintenance of bone integrity. Therefore, increasing the amount of fruit and vegetables may be necessary rather than reducing protein too much.
Therefore it is advisable to consume a normo-proteic diet rich in fruits and vegetables and poor in sodium, that is, a Mediterranean Diet-like eating patterns, eating foods with a negative acid load together with foods with a positive acid load. Example: pasta plus vegetables or meats plus vegetables and fruits (see figure below).

Alkaline Diet: Food and Acid Load
Fig. 1 – Food and Acid Load

Alkaline diet and muscle mass


As we age, there is a loss of muscle mass, which predispose to falls and fractures. A diet rich in potassium, obtained from fruits and vegetables, as well as a reduced acid load, results in preservation of muscle mass in older men and women.

Alkaline diet and growth hormone

In children, severe forms of metabolic acidosis are associated with low levels of growth hormone with resultant short stature; its correction with potassium or bicarbonate citrate increases growth hormone significantly and improves growth. In postmenopausal women, the use of enough potassium bicarbonate in the diet to neutralize the daily net acid load resulted in a significant increase in growth hormone and resultant osteocalcin.
Improving growth hormone levels may reduce cardiovascular risk factors, improve quality of life, body composition, and even memory and cognition.

Conclusion

Alkaline diet may result in a number of health benefits.

  • Increased fruits and vegetables would improve the K/Na ratio and may benefit bone health, reduce muscle wasting, as well as mitigate other chronic diseases such as hypertension and strokes.
  • The increase in growth hormone may improve many outcomes from cardiovascular health to memory and cognition.
  • The increase in intracellular magnesium is another added benefit of the alkaline diet (e.g. magnesium, required to activate vitamin D, would result in numerous added benefits in the vitamin D systems).

It should be noted that one of the first considerations in an alkaline diet, which includes more fruits and vegetables, is to know what type of soil they were grown in since this may significantly influence the mineral content and therefore their buffering capacity.

References

Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24(11):1835-40 [Abstract]

Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acid-ash diet hypothesis. Nutr J 2009;8:article 41 [Abstract]

Fenton T.R., Tough S.C., Lyon A.W., Eliasziw M., Hanley D.A. “Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis applying Hill’s epidemiologic criteria for causality.” Nutr J 2011;10:article 41 [Abstract]

Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630:7 pages doi:10.1155/2012/727630 [Abstract]

Potassium intake and cardiovascular risk factors

Potassium intake and health

In a study published on British Medical Journal a research team has conducted a systematic review of the literature and meta-analyses on potassium intake and health in apparently healthy adults and children without renal impairment that might compromise its handling.
Eleven cohort studies (127038 participants) reporting all cause mortality, stroke, cardiovascular disease, or coronary heart disease in adults and twenty-two randomized controlled trials (1606 participants) reporting blood lipids, blood pressure, renal function, and catecholamine concentrations were included in the study.
In adult with hypertension an increased potassium intake reduced systolic blood pressure by 3.49 mm Hg and diastolic blood pressure by 1.96 mm Hg.
No effect was seen in adult without hypertension (however, the studies were of relatively short duration and did not consider the effect that increased potassium intake may have over time) and in children (there is a lack of data in children: only three controlled studies with 156 partecipants).
There was no adverse effect of increased potassium intake on blood lipids, or catecholamine concentrations in adults whereas an inverse statistically significant association was seen between its intake and the risk of incident stroke (a 24% lower risk).
In healthy adult there was no significant adverse effect on renal function.
This study suggests that, in people without impaired renal function, increased potassium intake (at least 90 mmol/day) is potentially beneficial for the prevention and control of elevated blood pressure and stroke.

How to increase potassium intake

Potassium Intake: Fruits and Vegetables: Rich in Potassium
Fig. 1 – Fruits and Vegetables: Rich in Potassium

It should be noted that an increased potassium intake can be achieved following the largely plant-based Mediterranean Diet, which is characterized by the consumption of large quantities of fresh fruit, vegetable, legumes and unrefined cereals, all rich in potassium (that is also accompanied by a variety of other nutrients).

Aburto N.J., Hanson S., Gutierrez H., Hooper .L, Elliott P., Cappuccio F.P. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ 2013;346:f1378

Body fat: how to lose it and avoid regaining it

Body fat and daily caloric balance

The international scientific literature is unanimous in setting the lower limit for the daily caloric intake to 1200 kcal for women and 1500 kcal for men (adults).

Body Fat: Daily Caloric Balance
Fig. 1 – Daily Caloric Balance

To make negative the daily caloric intake, and therefore lose body fat, evaluation of actual caloric needs of the subject will be alongside:

This will make weight loss easier and protect from subsequent weight gains (body fat).
Ultimately, there must be a change in lifestyle.

Lose body fat and “miracle diets”

So, the best strategy for losing body fat is not a drastic reduction in caloric intake, nor follow constrictive or “strange” diets (such as hcg diet plan, sacred heart diet, paleo diet, Master Cleanse diet, the diet that Beyonce did, etc.) that require to eliminate or greatly reduce the intake of certain macronutrients, mostly carbohydrates.
Such conducts can be:

  • very stressful from psychological point of view;
  • not passable for long periods;
  • hazardous to health because of inevitable nutrient deficiencies.

Finally, they do not ensure that all the weight lost is only or almost only body fat and are often followed by substantial increases in body weight (weight cycling or yo-yo effect).
Why?

Body fat and excessive reduction of energy intake

An excessive reduction of energy intake means eating very little and this determines the risk, high, not to take adequate amounts of the various essential nutrients, that is, what we can’t synthesize such as vitamins, certain amino acids, some fatty acids and minerals, including e.g. calcium, essential for bone metabolism at every stage of life, or iron, used in many body functions as the transport of oxygen to the tissues. This results in a depression of metabolism and hence a reduction in energy expenditure.

Body fat and the entry in a “phase of famine/disease”

A excessive reduction in caloric intake is registered by our defense mechanisms as an “entry” in a phase of famine/disease.
The abundance of food is a feature of our time, at least in industrialized countries, while our body evolved over hundreds of thousands of years during which there was no current abundance: so it’s been programmed to try to overcome with minimal damage periods of famine. If caloric intake is drastically reduced it mimics a famine: what body does is to lower consumption, lower the basal metabolism that is consumes less and therefore also not eating much we will not get great results. It is as if a machine is lowered the displacement, it’ll consume less (our body burns less body fat).

Body fat and Carbs reduction

The elimination or substantial reduction in carbohydrate intake in the diet results in an increased intake of protein, fats and cholesterol because it will increase the intake of animal products.
In the body there are no amino acids reserves thus they are metabolized and, as a byproduct of their use, ammonia is formed and it’ll be eliminated as toxic; for this reason high-protein diets imply an extra work for liver and kidneys and also for this they are not without potential health risks.
An increased fat intake often results into an increased intake of saturated and trans fats and cholesterol, with all the consequences this may have on cardiovascular health.
What has been said so far should not induce to take large amounts of carbohydrates; this class of macronutrients should represent 55-60% of daily calories, fats 25-30% (primarily extra-virgin olive oil) and the remainder proteins: thus a composition in macronutrient that refers to prudent diet or Mediterranean Diet.

Body fat and excessive reduction in energy intake 

Whether the reduction in energy intake is excessive or even there are periods of fasting, it adds insult to injury because a proportion of free fatty mass will be lost.
Glucose is the only energy source for red blood cells and some brain areas (other brain areas can also derive energy from ketone bodies, which are a product of fatty acid metabolism) [at rest brain extracts 10% of the glucose from the bloodstream, a significant amount, about 75 mg/min., considering that its weight is about 1.5 kg]. To maintain a constant glycemia, and thus ensure a constant supply of glucose to tissues, we needs to take carbohydrates or alternatively amino acids, both easily obtained from foods.
In the case of a low or absent dietary intake of carbohydrates, whereas after about 18 hours liver glycogen, which releases glucose into circulation, depletes, body synthesizes de novo glucose from certain amino acids through a process called gluconeogenesis (actually this metabolic pathway is active even after a normal meal but increases its importance in fasting).
But what’s the main source of amino acids in the body when their dietary intake is low or absent? Endogenous proteins, and there is a hierarchy in their use that is before we consume the less important and only after the most important ones. For the first digestive enzymes, pepsin, chymotrypsin, elastase, carboxypeptidase and aminopeptidase (around 35-40 g) will be used; successively liver and pancreas slow down their synthesis activities for export proteins and unused amino acids are directed to gluconeogenesis. It’s clear that these are quite modest reserves of amino acids and it is the muscle that will undertake to provide the required amounts of amino acids that is proteolysis of muscle proteins begins.
Note: there is no absolute sequentiality in the degradation of several proteins, there is instead a plot in which, proceeding, some ways lose their importance and others will buy. So, to maintain constant glycemia the protein component of muscle is reduced, including skeletal muscle that is a tissue that represents a fairly good portion of the value of the basal metabolism and that, with exercise, can significantly increase its energy consumption: thus essential for weight loss and subsequent maintenance. It is as if the engine capacity was reduced.
One thing which we don’t think about is that heart is a muscle that may be subject to the same processes seen for skeletal muscle.
Ultimately make glucose from proteins (also food-borne) is like heat up the fire-place burning the furniture of the eighteenth century (amino acids) having available firewood (dietary carbohydrates).
Therefore, an adequate intake of carbohydrates with diet prevents excessive loss of proteins that is there is a saving effect of protein played by carbohydrates.
Mammals, and therefore humans, can’t synthesize glucose from fats.

In summary, the best way to lose body fat, that also protects against future increases, is to make negative the daily caloric balance increasing physical activity and controlling food intake, i.e. change your own lifestyle.

References

Cereda E., Malavazos A.E., Caccialanza R., Rondanelli M., Fatati G. and Barichella M. Weight cycling is associated with body weight excess and abdominal fat accumulation: a cross-sectional study. Clin Nutr 2011;30(6):718-23 [Abstract]

Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005

Sachiko T. St. Jeor S.T. St., Howard B.V., Prewitt T.E., Bovee V., Bazzarre T., Eckel T.H., for the AHA Nutrition Committee. Dietary Protein and Weight Reduction. A Statement for Healthcare Professionals From the Nutrition Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association. Circulation 2001;104:1869-74 [Abstract] [PDF]