What should we change in our diets in order to lose weight? It is estimated that at least half of the female population—and a few men who are scared by their doctors, family, friends or what they see when they look in the mirror—want to lose weight.
A telephone survey conducted by Thomson Reuters in the United States in 2010, on a sample of more than 100,000 people, revealed that 51.8% of respondents had tried to lose weight in the previous 12 months, and half of them intended to lose more than 10 kilograms[1]. Is this hunger to shed kilograms—which seems to have taken over the world—justified, or is it all, as Solomon might have said, meaningless, a toil, and chasing after the wind?
On the second day of this year, when the cabbage rolls, steaks, and other delicious leftovers from New Year’s Eve dinner had not yet been eaten and the guilt for eating excessively had begun to creep into the hearts of many, the prestigious medical journal JAMA (The Journal of the American Medical Association) published the results of a systematic analysis. On the same day, news channels broadcast the news that would restore the courage of the common man to at least finish their already cooked, fatty and tasty dishes—and even to prepare some more for the next holidays. It was not a study conducted on a handful of patients, but an analysis of 97 studies with a total of 2.88 million subjects, and involving over 270,000 deaths[2].
The conclusion? First degree obesity, in this collected sample, was not associated with a higher mortality rate. Overweight but not obese people even had a significantly lower mortality rate (regardless of the cause) compared to those with normal weight. People suffering from a more severe type of obesity (second and third degree) had a significantly higher mortality risk. The implied moral? It’s good to be a bit overweight because you will live longer. You can even be slightly obese, because the mortality risk will not be higher than for people with normal weight. “I believe the data,” said Elizabeth Barrett-Connor, a professor of preventive medicine at the University of California, in 2007, when the analysis was based on 2.3 million subjects. On that occasion, she expressed the opinion that the weight of overweight (but not obese) people “may be optimal.”
Is trying to lose weight worth it?
The JAMA article was not received as a reassuring revelation of truth, and immediately stirred up a reaction. Several experts rushed to draw attention to the study’s limitations, despite its impressive size. To summarise, the respective analysis used body mass index (BMI) to classify subjects. This index is somewhat of a necessary evil. One knows that, in some ways, it is a useful tool in the absence of a better one, but it has its limitations and does not always reflect reality (it does not take into consideration sex or ethnic differences, or the proportion between fat and muscular mass in the body). This is why it has been suggested that, to get an accurate picture, one should also use other measurements of the fat percentage in the body, like the waist circumference or waist-hip ratio. Furthermore, and perhaps even more importantly, the famous study only analysed the mortality rate, leaving out the morbidity, and the impact of being overweight and having grade 1 obesity on the quality of life, which could be significantly affected.
It is well-known that obesity is frequently associated with other diseases. The association between obesity, type II diabetes, and cardiovascular disease is a classic example, describing the coexistence of the three in the same patient. However, obesity seems to “contaminate” the body with new diseases, or to increase the risk for existing ones. More and more research tends to validate the observed connections, for instance, between obesity and asthma, many types of cancer (breast cancer in postmenopausal women[3], colon cancer, endometrial cancer, oesophageal cancer, renal cancer, gastric cancer, pancreatic cancer or leukaemia[4]), gout[5], chronic kidney disease[6], acute respiratory distress syndrome, and polycystic ovarian syndrome (where obesity is not a cause, but increases the risks and makes treatment more difficult[7]).
Quality of life can also be affected by aspects which have nothing to do with one’s health. Many people cannot refrain from making mean jokes on account of people’s high body weight for their height and age. Children are more exposed to the insensitive jokes of other children their age, but even adults are not indifferent to words, gestures, or even simple, double-meaning smiles.
Even doctors seem to be less willing to treat obese patients with as much respect, understanding, and empathy as patients with normal body weight. At least this is what is suggested by an article published by a group of researchers at the John Hopkins University in the US.[8] This is not to mention the cultural pressure exerted on women, who always feel the need to lose one or two pounds. It’s no wonder that many people are trying to lose weight. For this, dozens, perhaps hundreds of diets and weight loss recipes have been promoted and tried.
The diet fair
Diets and weight-loss secrets are everywhere: in newspapers and magazines, in books, on TV and the radio, on the internet, in the train, on hand-written pieces of paper exchanged between friends and strangers. Dozens of books (or perhaps hundreds) are published each year[9], promising the buyer the much-desired success. Some are written by experts, people with academic titles or PhDs in nutrition or other related fields, others by unqualified people who discovered a recipe and tested it out on themselves. Some are written in a balanced way, according to current scientific knowledge, while others are projections of the author’s fantasy. By following some, you can lose weight or, at worst, you can lose the money you paid for the books. By following others, you can lose your health.
If some diets are limited to general principles, recommending a certain number of calories, physical exercise or permitted vs forbidden foods, others are complex and insist on certain foods, on certain days of the week, at certain mealtimes. In other words, some are flexible while others are inflexible.
The diets’ vast “arsenal”Some books even promise that, if you buy them and strictly follow their advice, you will lose weight by eating whatever, and however much, you want. Many start by demonstrating that the author knows what you’re going through: you’ve already tried to lose weight dozens of times before and failed or, if you succeeded, you soon regained the extra kilos. The book you are holding promises that this time it will be different: you will reach the promised land of losing weight without pain and starvation, and on your way to this land you will not turn into a snarling, desperate dog. On the contrary, you will feel great! Some explain why everything you have been trying so far has failed: first, because losing weight must begin not with what and how you eat, and how much physical exercise you do, but from your own self-beliefs (you have to start with the mind). Second, because avoiding carbohydrates is not the recipe for success, but succeeding in eating less calories, and following the plan that has been set out (a plan that promises to yield results in only 4 weeks, according to the cover). Third, because you do not need to lose weight but eat less. Others says that the key lies in exercising more, or that modern foods are nutrient-deficient. Some say that the secret lies in sleeping better or giving up salt, and so on and so forth. Some include 50, 177, or 1001 ways to lose weight. Others promise that you will lose weight eating whatever you like: chocolate, french fries, and cakes (but when you read the book you learn that you can only do this twice a week, or two days a year). |
All diets come down to a few core principles
Despite the large diversity in names and food schemes, all these diets have certain common characteristics that can be grouped into distinct categories: (a) diets with a moderate, low or very low fat content; (b) protein-rich diets; (c) low carb diets and (d) low glycaemic index diets[10].
When it comes to diets with a moderate fat content, 35-45% of the calories come from lipids. The so-called Mediterranean diet is sometimes included in this category. However, seeing that Mediterranean diets may vary considerably, one must not implicitly believe that any Mediterranean diet has a moderate fat content. For diets with a low fat content, 20-35% of the calories are from lipids. These are recommended by several authorities or medical associations, but also by some commercial programs like Weight Watchers, for instance. In the case of diets with a very low fat content, just 10-20% of the total amount of calories come from lipids (here we can include the Pritikin and Ornish diets).
Protein-rich diets are considered to provide at least 25% of total energy requirements from protein foods. These diets resemble low carb diets (which also contain high amounts of protein), but are different in the sense that they are poor in fats (low carb diets are relatively rich in fats). The Zone diet (30% protein, 40% carbs, 30% fats) is an example of a protein-rich diet.
Low carb diets have a low caloric content of carbohydrate origin (about 10%, gradually increasing over time), but a relatively high content of lipids (around 60%). This is what sets them apart from protein-rich diets, which are relatively low in fats. They are also called ketogenic diets because, by metabolizing lipids, they cause the accumulation in the body of substances called ketone bodies. Probably the best known diet in this group is the Atkins diet (“The revolutionary new Atkins diet”) but we can also include others here: South Beach, Dukan, Paleo (or Paleolithic because it tries to reproduce the alleged content of human diets in the Paleolithic age), and others.
Low glycaemic index diets include foods with a glycaemic index below 55.[11] The glycaemic index (GI) is measured on a scale from 0 and 100, and synthetically expresses the effect of food on blood glucose levels. Foods with a low glycaemic index are digested and absorbed slowly. They slowly change the level of blood glucose (blood sugar) and insulin, thus having a beneficial effect on health. On the contrary, those with a high glycaemic index are rapidly absorbed and cause rapid and abrupt fluctuations in blood sugar and insulin. The glycaemic index applies only to foods relatively high in carbohydrates (it does not apply to meat, eggs, most vegetables, and greens)[12]. Low-glycaemic foods include most whole grains, legumes, non-starchy vegetables (including carrots) and fruits[13].
What is the best diet for weight loss?
Many of the fanciful diets (such as the “apple diet” or the “nettle diet”) have not been scientifically evaluated, but the main types, as presented above, have been investigated in several clinical trials that allow us to draw some conclusions—although there are still questions waiting to be answered. Analysing the studies published so far shows that all diets (low fat, high in protein, low carbs, with low glycaemic index) can contribute to weight loss, possibly most pronounced in the case of ketogenic diets. Each of them also tends to improve health, in particular, by reducing the risks of cardiovascular disease and type II diabetes[14],[15]. However, there are relatively few studies on the long-term effects of these diets, and existing studies tend to show that their effects on weight loss are much lower in studies of longer duration[16]. In the case of ketogenic diets (diets low in carbohydrates) there are also concerns about the long-term effects on the body[17], so the American Society of Cardiology, for example, is against these diets[18].
However, perhaps the most important aspect related to these diets is that studies frequently show that subjects fail to adhere to their chosen diet in the long run, and their body weight almost always starts to increase again. The data available so far indicates that there is an association between diet and weight loss, so the above question may be wrong. It seems that sticking to a certain diet[19] is more important than the diet rush, or, finding out what the ideal diet is. The chosen diet must be balanced from a nutritional point of view, and should not strain the body’s nutritional needs. We must also not forget that, although dietary control is essential for body weight control, physical effort plays an equally important role[20]. Trying to lose weight with a controlled diet, but without exercise, is like trying to fly with only one wing.
Robert Ancuceanu, PhD, is a professor in the Faculty of Pharmacy at the Carol Davila University of Medicine and Pharmacy in Bucharest, Romania.
