In the phase of weight loss, as during weight maintenance, it is important to maintain as constant as possible the daily energy expenditure.
Indeed, daily caloric consumption usually decreases during weight loss.
Since the 90s of last century, it has been proposed that green tea, thanks to its content of caffeine and catechins, particularly epigallocatechin gallate (EGCG), which are also present in oolong tea and white tea, could be of help for:
maintaining , or even increasing, the daily energy expenditure;
increasing fat oxidation, thus acting as a fat-burning food.
Therefore, it was attributed to green tea the ability to cause a fat loss, and so to be of help for overweight or obese adults in achieving the ideal weight.
In addition to these potential lipolytic and thermogenic effects, catechins and caffeine may be useful by acting on other targets, such as the intestinal absorption of fat and the energy intake, probably through their impact on the gut microbiota and gene expression.
Therefore, products for weight loss and weight maintenance based on green tea extracts have been marketed. It should be noted that these products contain catechins and caffeine in amount much greater than the classic drink.
How much truth is there in green tea “fat burning” properties?
The issue seems to have been resolved by a careful meta-analysis of 15 studies on weight loss and intake of these “fat burning” products.
Eight of the 15 analyzed studies were conducted in Japan, and the rest outside of Japan, for a total number of 1945 subjects, which were followed for a period of between 12 and 13 weeks.
The study showed that the consumption of green tea-based products induces, in overweight and obese adults, a weight loss that is:
not statistically significant;
probably not clinically important.
These “fat burning” products have not proved to be useful not even in weight maintenance.
Thus, on the basis of scientific evidence, green tea does not seem to be helpful in fat loss nor in weight maintenance.
There are no magic bullets: the only way to lose weight (body fat) and avoid future increases is to control your daily calorie intake and take part in physical activity on a regular basis.
Hursel R. and Westerterp-Plantenga M.S. Catechin- and caffeine-rich teas for control of body weight in humans. Am J Clin Nutr 2013;98:1682S-1693S [Abstract]
Hursel R., Viechtbauer W. and Westerterp-Plantenga M.S. The effects of green tea on weight loss and weight maintenance: a meta-analysis. Int J Obesity 2009;33:956-961 [Full text]
Jurgens T.M., Whelan A.M., Killian L., Doucette S., Kirk S., Foy E. Green tea for weight loss and weight maintenance in overweight or obese adults. Editorial group: Cochrane Metabolic and Endocrine Disorders Group. 2012:12 Art. No.: CD008650 [Abstract]
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).
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.
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. How?
Body fat, reduction in energy intake and role of carbohydrates
Glucose is the only energy source for red blood cells and some brain areas, while 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 muscleproteins begins.
Note: Anyway, 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, namely, there is a saving effect of proteins played by carbohydrates.
Mammals, and therefore humans, can’t synthesize glucose from fats.
The elimination or substantial reduction in carbohydrate intake in the diet results in an increased intake of proteins, fats and cholesterol because it will increase the intake of animal products, one of the main defects in hyperproteic diet.
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 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).
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.
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. doi:https://doi.org/10.1016/j.clnu.2011.06.009
Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005
Ravussin E., Lillioja S., Knowler W.C., Christin L., Freymond D., Abbott W.G.H., Boyce V., Howard B.V., and Bogardus C. Reduced rate of energy expenditure as a risk factor for body-weight gain. N Engl J Med 1988;318:467-72.doi:10.1056/NEJM198802253180802
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. doi:https://doi.org/10.1161/hc4001.096152
If the situation eludes our control it is possible, indeed probable!
Only a few stubborn people will be able to lose weight in this period; instead for “all of us” a good result will be “damage limitation” and we succeed in doing so only if we will not fill our homes to the brim with dainties which we can’t resist (we are putting enemies in our home!); Pandori, Panettone, chocolate, dried fruit, cured meats etc. etc. that will put us through the mill for weeks and weeks and in the end they’ll win……
Except Christmas Eve and Christmas dinner, however, where it is not advisable to exceed, in the remaining holidays we should attempt to eat as healthy as possible meanwhile keeping a good level of physical activity.
In fact it is good practice to remember that we don’t increase our weight from Christmas day to St. Stephen’s day but from St. Stephen’s Day to Christmas day.
Weight cycling or yo-yo effect, i.e. repeated phases of loss and weight gain, appears related to excess weight and accumulation of fat in the abdomen.
Yo-yo effect and health
Several studies suggest a link with increased blood pressure, increased blood cholesterol, with gallbladder disease, with a significant increase in binge eating disorder, in women with greater easy to weight gain than those who are not subject to weight cycling. In this regard there should be emphasized that the weight cycling occurs over years, during which, aging, the rate of metabolism inevitably tends to decrease: this could make more difficult the subsequent losses.
Finally, weight cycling was also associated with a sense of depression with regard to weight.
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]
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]
In order to maintain body weight: adjust caloric intake according to consumption
In order to maintain your body weight, energy intake with foods must match your individual needs, depending on age, sex and level of physical activity; calories exceeding needs accumulate in form of fat that will deposit in various parts of the body (typically in men, as in postmenopausal women, the accumulation area for excellence is abdomen).
An example: let’s assume an energy requirement of 2000 kcal with an intake of 2100 kcal. The extra 100 kcal could result from 30 g of pasta or 35 g of bread or a 25 g package of crackers or 120 g of potatoes or 10 g of oils from any source etc., not a particularly large amount of food. This modest calories surplus, if performed daily for one year leads us to take:
100 kcal x 365 days = 36500 kcal/year extra calories compared to needs.
Since a kilogram of body fat contains approximately 7000 kcal, if we assume that 36500 kcal in excess accumulate exclusively in form of fat (very plausible approximation), we obtain: 36500/7000 = about 5 kilogram of body fat.
So, even a modest daily calorie surplus, over a year, can lead to a substantial body weight gain in the form of fat mass.
This example shows the importance of estimating with accuracy our daily energy requirements.
In order to maintain body weight: split daily caloric intake into multiple meals
Let’s assume that daily caloric requirement to maintain body weight is equal to 2000 kcal.
Is it the same thing if they are consumed in just two meals, maybe dividing them in half between lunch and dinner, or is it advisable to take three to five meals during a day?
In order to mantain body weight, the best choice is to divide calories into five meals: breakfast, lunch and dinner, the most abundant, plus two snacks, one on mid-morning and the other on mid-afternoon. Why? There are various reasons.
Consuming only two meals during the day, lunch and dinner or breakfast and dinner, it is likely to approach both meals with a hunger difficult to control; we eat what we have on our plate already thinking about what else to eat, having the feeling of not being able to satisfy the hunger. We eat, but there is always room for more food. Among the reasons for this there are too many hours between meals. Two examples:
dinner at 8:00 p.m. and, the next day, lunch at 1:00 p.m.: the interval is 17 hours, more than 2/3 of a day;
breakfast at 7:00 a.m. and dinner to 8:00 p.m., 13 hours have passed, most of which are spent in working activities and therefore more energy-consuming than hours of sleep.
Then, drops in blood sugar levels (glycemia) can also occur: liver glycogen stores, essential for maintaining normal glycemia, with time intervals between meals previously seen, can easily reach values close to depletion.
Therefore, by splitting the daily caloric intake into two meals, it is most likely difficult to meet the target of assuming 2000 kcal (the suggested daily calorie intake).
The concentration of too many calories in a single meal may promote the increase of plasma triglycerides, the excess of which is linked to the onset of cardiovascular disease.
When accumulating almost all or all of the calories in just two meals we are likely to grow stout, have feelings of bloating and getting real digestive problems due to excess of ingested food, not to mention that could occur even a postprandial sleepiness or difficulties in getting asleep.
In order to maintain body weight: exercise regularly
Physical activity has a central role both in maintaining the reached body weight and in the loss of fat mass.
Make physical activity on a regular basis has several advantages.
If exercise is conducted on a regular basis and is structured in the proper way, is possible that, even without appreciable changes in weight, a redistribution of fat occurs between fat mass, which drops, and free fat mass, which, on the contrary, increases. Such a result can’t obviously be reached by simple walk; we need a specific training program, better if planned by a professional, and a proper diet, always of Mediterranean type.
We protect muscle mass (and as suggested in point 1. we can also increase it).
We maintain a high metabolism.
Muscle burn energy during and especially after exercise.
The body is toned.
Appetite is controlled more easily.
Making physical activity on a regular basis makes the prevention of weight gain easier, due to the inevitable “escapades” (indulging in a bit of chocolate, an ice cream etc..).
Giampietro M. L’alimentazione per l’esercizio fisico e lo sport. Il Pensiero Scientifico Editore. Prima edizione 2005
Shils M.E., Olson J.A., Shike M., Ross A.C.: “Modern nutrition in health and disease” 9th ed. 1999
Biochemistry and Nutrition