On a relaxed evening with friends, one of them commented that he wanted to lose weight. He had already cut out sugar and was exercising regularly, but he wanted to know the most efficient diet to achieve his goal.
I could end the article here with the answer I provided:
“There is no diet superior to another; we have several dietary approaches that can adapt to your needs and lifestyle. The ideal would be an individualized plan from a qualified professional."
Although my answer is very close to common sense, the doubt that motivated the question is real. Who has never, after a few years of reckless eating, daily stress, and a sedentary lifestyle, noticed an increase in fat and, instead of seeking guidance from a nutritionist, decided to save money and turn to Dr. Google?
It is common for these searches to result in sensational articles discussing the latest fad diet and its benefits or the method used by an actor to lose 60 pounds in 6 months. Unfortunately, these articles are often enough to motivate someone to replicate it, and, as happens in most cases, they end up giving up after a few months.
Diet Trends According to Google
Delving deeper into the subject, a 2020 study published in the journal Nutrition aimed to classify the most popular diets among Google users globally and regionally and analyze secular and seasonal trends.
Researchers used Google Trends (GT), a tool that provides access to an essentially unfiltered sample of real searches made on Google, to identify and analyze the evolution over time and regional interest in 47 diet-related topics. The topic "Mediterranean diet" was used by the researchers as a “benchmark” due to the evidence pointing to the beneficial effects of following this eating pattern, serving as a reference for calculating the interest in all topics in proportion to the overall relative search volume (RSV).
In terms of RSV, veganism showed 19.54 times more interest than the Mediterranean diet, followed by vegetarianism (15.09), gluten-free (11.11), low-carbohydrate (9.80), and ketogenic (6.27).
Of the 250 regions analyzed, veganism was the diet of greatest interest in 23 countries (including the United States, Mexico, and Italy), followed by vegetarianism in 14 countries, and both the ketogenic and low-carbohydrate diets in 7 countries.
The popularity of diets waxed and waned. Diets like the 5:2, raw veganism, juice fasting, and paleo followed fad patterns, rising and falling. Low-sodium, low-protein, and lacto-ovo vegetarian diets maintained steady interest. Notably, searches for 31 topics peaked in January, likely tied to New Year’s weight-loss resolutions, and were lowest in December, coinciding with festive celebrations.
The authors concluded that Google Trends was valuable for investigating local and international nutritional interests.
However, as usual, there are some crucial limitations to consider. Google Trends is used primarily by young people and women, making it less generalizable. Significant regional distinctions exist; 60-65% of United States users search on Google, while this exceeds 90% in some European countries. And now all diets are trending, e.g., Weight Watchers or MIND.
Before you search for the "best diet,” perhaps we should consider a source other than Dr. Google – doctors with training in nutrition, rather than search trends.
What is the most effective diet?
Although many studies and systematic reviews demonstrate the effectiveness of different diets for weight loss, few studies have compared which is the most effective. To address this question, a systematic review in the British Medical Journal sought to determine the relative effectiveness of macronutrient dietary patterns and popular diet programs for weight loss and improving cardiovascular risk factors in overweight or obese adults. I have written previously on the efficacy of diets on cardiovascular risk and will focus now solely on weight loss.
The authors searched databases for randomized studies on overweight or obese adults who followed a popular diet compared to an alternative or usual diet, focusing on weight loss and changes in lipid profiles and blood pressure over at least three months. Diets were categorized by their nutritional composition (low carbohydrate, low fat, and moderate macronutrients), brand names, or funding sources. Eligible studies allowed for physical exercise, behavioral support (e.g., counseling or group support), and meal replacements, provided they mainly included whole foods without medication use. The usual diet served as the comparison.
The final analysis consisted of 137 articles, of which 121 were RCTs, involving 21,942 participants, with an average age of 49 years, primarily women (69.0%), with an average BMI of 33.0 (indicative of mild obesity), with an average intervention duration of approximately 6.5 months. [1]
Overall comparisons between popular and usual diets for weight and blood pressure outcomes provided evidence of “moderate certainty.” However, when comparing popular diets with each other, the evidence was classified as “low certainty.”
At six months, low-carbohydrate diets led to an average weight loss of 4.63 kg compared to the usual diet, while low-fat diets resulted in a loss of 4.37 kg, and moderate macronutrient diets, i.e., Jenny Craig, Mediterranean, Weight Watchers or DASH, led to a loss of 3.06 kg. However, at the 12-month follow-up, average weight loss across all nutritional compositions diminished to 1 to 2 kg compared to the usual diet.
Focusing on popular dietary programs, the analysis after six months found that:
- The Jenny Craig diet (which provides meal replacements with low-calorie options and assistance from coaches) and the Atkins were the most effective, with average weight losses of 7.77 kg and 5.46 kg, respectively.
- Other diets, such as Ornish (average weight loss of 3.64 kg), Weight Watchers (3.90 kg), low-fat diets (4.85 kg), and the Mediterranean diet (2.87 kg), were less effective ones but still better than “dietary guidance” (0.31 kg).
Nevertheless, these weight losses tend to disappear over time. After 12 months, all diets seem to offer some benefit, but the average weight loss is almost uniformly similar, about 1 kg. In the end, the choice of one over another becomes largely irrelevant.
However, the review had two critical limitations. Many comparisons provided low-certainty evidence, primarily due to inconsistency, imprecision, and risk of bias. More importantly, little information was reported on adherence to the diets, and as many of us know from personal experience, adherence gets more difficult over time.
Again, we are faced with a question that has not yet been resolved. I would suggest the reason is simple; there is probably no single correct answer.
According to all available research, weight loss will occur if you use more calories than you consume, regardless of the dietary strategy. However, achieving this on your own is more complicated than it seems. For calories, it’s easy to underestimate how much we consume and overestimate how much we expend.
In light of the above, the best explanation on this subject is provided by Steven Novella.
“The short answer to any question about – does diet X work? – will always be: yes and no. … Diets statistically work in the short term because when you pay attention to your calorie intake and the exercise you perform, you are likely to consume fewer calories, which can result in weight loss.
… What the study [of intermittent fasting] tells us is that regular sessions with a nutritionist, weighing yourself, and paying attention to what you are eating (the general effects) will likely help you lose weight. It also demonstrates that the details of the diet strategy, such as macronutrient composition or timing of eating (the specific effects), do not matter as much or have very small effects.“
[1] Among the popular dietary programs analyzed, Atkins, Zone, DASH, Mediterranean, Paleolithic, Low Fat, Jenny Craig, Volumetrics, Weight Watchers, Rosemary Conley, Ornish, Portfolio, Biggest Loser, Slimming World, South Beach, and Dietary Advice
Sources: Global and local diet popularity rankings, their secular trends, and seasonal variation in Google Trends data. Nutrition. DOI: 10.106/j.nut.2020.110759
Comparison Of Dietary Macronutrient Patterns Of 14 Popular Named Dietary Programmes For Weight And Cardiovascular Risk Factor Reduction In Adults: Systematic Review And Network Meta-Analysis Of Randomised Trials BMJ. DOI: 10.1136/bmj.m696.
