Keto, Intermittent Fasting, Oat Milk: Separating Trend from Evidence
Every year brings new dietary trends to Irish supermarket shelves and social media feeds. Here's what the research actually shows about the ones that have lasted.
Dietary trends follow a predictable cycle: they emerge from a combination of genuine research, social media amplification, and industry interest; they peak; the evidence base is scrutinised more carefully; and most either fade or settle into a smaller, more accurate role in nutritional thinking. The problem is that the cycle takes years, and the original claims tend to be remembered more clearly than the subsequent qualifications.
Here's where the current evidence actually sits on the trends that have dominated Irish nutrition conversation recently.
Ketogenic Diets
The ketogenic diet - very high fat, very low carbohydrate - does produce short-term weight loss, largely through water loss and appetite suppression from ketone production. The evidence for its long-term superiority over other approaches is less convincing. A landmark trial published in the New England Journal of Medicine found that at 12 months, low-carbohydrate diets produced similar weight loss to low-fat diets with similar dropout rates. More recent meta-analyses have largely confirmed this: the diet works, but not more than other structured approaches.
The genuine evidence base for keto is strongest in clinical contexts: it remains a first-line treatment for certain forms of drug-resistant epilepsy, and there's emerging evidence for its role in managing Type 2 diabetes under medical supervision. As a general weight-loss approach for otherwise healthy adults, the evidence suggests it's effective but not uniquely so - and adherence over 12+ months is typically poor.
Intermittent Fasting
Intermittent fasting - particularly the 16:8 approach (eating within an 8-hour window) - has attracted significant research interest. The evidence is more positive here than for many trends. A 2019 review in the New England Journal of Medicine summarised evidence suggesting that time-restricted eating patterns are associated with metabolic benefits independent of calorie restriction. However, a 2022 CALERIE trial found that most of intermittent fasting's benefits appear to be attributable to reduced calorie intake rather than the fasting pattern itself.
The practical takeaway: for people who find skipping breakfast and eating within a window easier than counting calories, intermittent fasting is a valid approach. It's not metabolically special, but it is a sustainable calorie reduction strategy for some people.
Plant-Based Eating (vs. Fully Vegan Diets)
There's a meaningful distinction between the growing interest in plant-forward eating and the more specific claims made for fully vegan diets. The evidence for increasing plant food consumption - vegetables, legumes, whole grains, nuts - is consistently strong across decades of research. Mediterranean dietary patterns, which emphasise plants without excluding animal foods entirely, have the strongest long-term evidence base of any dietary pattern.
Fully vegan diets require more careful planning, particularly around Vitamin B12 (supplementation is essential), Vitamin D, iron, iodine, and omega-3s. Safefood Ireland's guidance on vegan diets is clear that these aren't concerns that affect everyone equally - but they're real and worth addressing rather than dismissing.
Oat Milk and Plant-Based Dairy Alternatives
Oat milk's rise has been remarkable. It's now the most popular plant-based milk in Ireland by volume sold. Nutritionally, it's a different product to cow's milk - lower in protein (typically 1g per 100ml vs 3.4g in whole milk), similar in calories, lower in calcium unless fortified. The Safefood guidance on dairy alternatives recommends choosing fortified versions specifically for calcium and iodine, both of which are naturally present in cow's milk but not in oat milk.
For most adults, swapping to oat milk is nutritionally fine with appropriate substitution elsewhere. For children under 5, the HSE still recommends whole cow's milk or first-choice plant alternatives (fortified soy milk) rather than oat milk as a primary milk source, due to the protein and fat differences.
The Mediterranean dietary pattern - rich in vegetables, legumes, whole grains, and olive oil with moderate fish and dairy - has the strongest long-term evidence base of any named dietary pattern in the research literature. [NIH/NEJM review, 2013]