In Search of the ‘Holy Grail’ of Dieting

Statistics investigated 10,085 participants in the US between July 2023 and June 2024 about the diet or nutritional guidelines they follow.

• 52% do not adhere to nutritional rules.
• 17% follow a low-carb or carbohydrate-free diet.
• 11% avoid dairy products or products containing lactose.

Of course, we don’t know what the motivations behind these choices are. Are they due to health issues (such as lactose intolerance), weight loss efforts, or a desire for a healthier lifestyle?

Research An online survey of 1,005 Americans published in 2022 by the International Food Information Council (IFIC) found:

• 52% of Americans reported following a specific diet or eating pattern in the past year, a significant increase from previous years.
• The most common diets were clean eating (16%), mindful eating (14%), calorie counting (13%), and a plant-based diet (12%), with low-carb coming in seventh (6%).
• The main motivations were protecting long-term health (35%), losing weight (34%) and feeling better and having more energy (31%).

Based on these two studies, we can conclude that diet and nutrition are of great interest to the general population, and that there is a striking difference in the types of diets that people follow. While the Statista study emphasized low-carb diets, the IFIC study emphasized clean eating.

The public, lacking the proper knowledge, turns to sources like Dr. Google for information. This can lead to questionable quality information based on the website or influencer they follow.

Diets: There’s No Shortage of Options

We can define a diet as a regimen or plan designed for a specific individual, taking into account their goals and unique physical, socioeconomic, and cultural characteristics. While this definition is simple, it can be difficult to identify the “best” diet strategy from the many options available without professional help.

For example, US News Health published their ranking of 30 different diets as the Best Diets in 2024Their criteria included:

• Nutritional Completeness
• Health risks and benefits
• Long-term sustainability
• Evidence-based effectiveness
• Strengths and weaknesses of each diet
• Specific goals that each diet can meet more effectively

The three best “overall” diets were the Mediterranean diet (rich in vegetables, whole grains, olive oil, fish, and minimal red meat), the DASH diet (similar to the Mediterranean diet but lower in sodium), and the MIND diet (a combination of the Mediterranean and DASH diets aimed at preventing cognitive decline).

While this ranking reflects expert opinion, it is not definitive scientific evidence for the healthiest diet.

Which diet is the healthiest?

Given the Mediterranean diet’s reputation as the “best diet overall” and the frequent praise in news reports of its health benefits, a systematic review and meta-analysis is particularly useful to answer this question.

Published in the British Medical Journal in 2023, this judgement aimed to determine the relative effectiveness of structured dietary programs and healthy behavior programs in preventing death and major cardiovascular events (MACE) in patients at increased risk of cardiovascular disease.

The analysis included only randomized clinical trials that included at least nine months of intervention in adults with cardiovascular disease or two risk factors that compared a structured diet program with reported MACE. These structured diet programs could include non-diet interventions, such as exercise, psychosocial or behavioral support, as well as smoking cessation and drug treatments.

In total, 40 studies were considered adequate, with 35,548 participants. The average follow-up time was three years. [1] The diet programs include:

• 18 studies using a low-fat diet program
• 6 Studies Using a Very Low-Fat Diet Program
• 4 studies used a combination of low-fat and low-sodium diets
• 6 studies followed a modified fat diet
• 12 studies used the Mediterranean diet
• 3 studies used the Ornish diet, basically a plant-based diet
• 1 study used the Pritikin diet, which emphasizes whole foods

The quality of the research into the sole The effect of the diet was attenuated in low-fat and Mediterranean diet programs due to co-interventions and in two studies with indirect estimates of their impact.

• Evidence showed that the Mediterranean diet program was better than minimal intervention in reducing overall mortality. Participants who followed the diet were 28% less likely to die. That benefit increased as the patient’s risk increased.
• The Mediterranean diet was also shown to be better at reducing cardiovascular deaths, nonfatal heart attacks and strokes.

• Evidence showed that the low-fat diet program was better than “minimal intervention” in reducing overall mortality. Participants following this diet were 16% less likely to die from any cause. This diet was the only one that reduced the incidence of unplanned cardiovascular interventions.
• The combined low-fat and low-sodium diet appears to have benefits in reducing the risk of stroke in high-risk patients.

• When adjusting for covariates such as exercise, stress management support, smoking cessation, and medication treatment, there were no substantial differences in nutritional outcomes.

The authors conclude that dietary programs promoting Mediterranean and low-fat diets – with or without exercise or other interventions – can reduce all-cause mortality and nonfatal myocardial infarction in elderly patients at increased cardiovascular risk. However, there is no convincing evidence that the Mediterranean diet is better than the low-fat diet in preventing these outcomes.

However, before you increase your intake of olive oil, omega-3-rich fish and whole grains and reduce your red meat consumption (which is still good advice), it’s important to acknowledge that the study had some important limitations.

The main limitation of this review is the inclusion of diet programs with co-interventions, such as drug treatment and smoking cessation, which makes it difficult to identify the true role of the diets in the observed outcomes. If these co-interventions had been provided to both the control and intervention groups, this would have reduced the risk of bias. Furthermore, the researchers highlight the difficulty in analyzing adherence to diet programs.

An uncomfortable, inconclusive conclusion

Based on the evidence presented in the review and its limitations, the question of which diet is healthiest remains open. While this may be a disappointing conclusion, it is the most realistic one.

What we can deduce is that a balanced and structured diet based on generally healthy foods is likely to be more effective than doing nothing or very little when considering healthy choices. However, the precise composition of such a diet, let alone personalizing it to your needs, requires further exploration.

Ultimately, the review agrees with common sense: healthy eating is just one part of a healthy lifestyle. A lifestyle that includes physical exercise, stress reduction, smoking cessation, and, if necessary, drug therapy, all of which reduce mortality and cardiovascular risk — something that is pretty obvious, by the way.

[1] Regarding methodological quality, 13 studies were classified as having a low risk of bias, while 27 studies were classified as having a high risk of bias.

Source: Comparison of seven popular structured diet programs and the risk of mortality and major cardiovascular events in patients at increased cardiovascular risk: systematic review and network meta-analysis. BMJ DOI: 10.1136/bmj-2022-072003.