In a landscape saturated with nutritional discourses, methods that promise miracles and polarised narratives that change every six months, scientific evidence is once again bringing order. And this time it does so with a clinical study rigorously designed that answers one of today's most relevant questions: Which dietary strategy works best for weight loss, and which can really be sustained in the long term?
The research, led by the Dr. Francisco J. Tinahones from the Obesity, Diabetes and its Comorbidities group, directly compared - and with a level of control unusual in nutritional trials - five different approaches: the classic hypocaloric diet, the ketogenic diet, modified alternate-day fasting, and two modes of time restriction (avoiding breakfast or avoiding dinner). For three months, 160 obese adults followed these strategies under medical supervision. The result: an accurate portrait of what works, how much and for whom.
The conclusions are clear. The alternative strategies - ketogenic, modified alternate fasting and time restriction - were significantly more effective in the short term. than the classic low-calorie diet spread over 3-4 meals. The greatest weight loss was achieved by the ketogenic group, with almost 12 kilos in three months, followed by the alternating fasting and the restricted eating schedule. All, however, shared a Mediterranean nutritional base and strict calorie control.
But the most interesting fact is not just how much weight is lost, but how it is lost. Modified alternate fasting - alternating a day of normal intake with a day of sharp calorie reduction - was the method that most reduced body fat, a parameter directly related to metabolic risk, systemic inflammation and accelerated ageing. Late time restriction (avoiding dinner) also showed a clear improvement in body composition, in line with what we already know about circadian rhythms and nocturnal metabolism.
And yet, the real value of this data emerges when we analyse its sustainability. Because any strategy works for weeks; the difficult thing is to sustain it for months or years without falling into the rebound effect.
The ketogenic, Despite its initial efficacy, it is one of the least adhered to diets in the long term. Its severe carbohydrate restriction is difficult for many people and, in practice, it can only be maintained as a temporary intervention or evolve into a more flexible, Mediterranean low-carbohydrate version.
Modified alternate-day fasting, The 16:8 window, brilliant for accelerating results, requires a very stable personal and professional structure. Most people who adopt it during a period of weight loss end up transitioning to more sustainable 16:8 or 14:10 windows.
The time restriction, especially when the late dinner is avoided, has the best adherence in long-term studies. It is aligned with circadian rhythms, does not require elimination of food groups and integrates naturally into modern lifestyles.
Traditional hypocaloric, While less impactful in the short term, it is still surprisingly robust when implemented with nutrition education, dietary variety and professional accompaniment. It is not the fastest, but it is one of the most stable.
What does this tell us from a wellness, holistic health and longevity perspective? That short-term effectiveness and long-term sustainability are not the same thing.. And that the best approach is probably not to choose between one diet or another, but to integrate strategies.
Rapid interventions - ketosis, alternate fasting, intensive calorie restriction - can serve as metabolic accelerators. Shock tools for people with obesity who need precise and measurable changes. But the real maintenance occurs when, after this initial boost, a transition is made to a Mediterranean pattern that is anti-inflammatory, flexible, rich in micronutrients, adjusted to the rhythms of the day and compatible with real life.
In Dr Tinahones“ own words, these data invite us to ”broaden the range of nutritional approaches, adapting them to the characteristics and needs of each patient". And that is exactly the direction in which modern nutrition is heading: less dogma, more personalisation. Less prohibition, more strategy. Less obsession with rapid loss and more focus on resilient, functional and sustainable metabolism.
In a world where obesity threatens to affect 50 % of the world's population in just a decade, studies like these don't just inform: they transform. And they remind us that true health does not come from a specific diet, but from understanding the body, respecting its rhythms and building a lifestyle that we can sustain over time without giving up vitality, wellbeing or the pleasure of living.
