The fat pathway: they are good for you and are a source of energy for athletes

IN BRIEF

• Fats are not "bad" substances: they perform structural functions, transport fat-soluble vitamins, and provide dense energy.
• The quality of fats (mono- and polyunsaturated vs. trans) is more important than just the quantity for cardiovascular health.
• In endurance sports, fats are a primary energy source for prolonged efforts: their use depends on intensity, training, and diet.
• Sources rich in unsaturated fats — extra virgin olive oil, oily fish, nuts, and seeds — are associated with favorable cardiovascular risk profiles.
• Evidence is largely consistent with benefits when saturated fats are replaced with unsaturated fats; methodological limitations remain, and different contexts require cautious interpretation.

Abstract: what does science say?

Dietary fats (lipids) are essential nutrients: they build cell membranes, transport fat-soluble vitamins, and provide a highly concentrated energy source. In recent decades, research has shifted its focus from the general demonization of fats to evaluating their quality and their role as substitutes in the diet: replacing saturated fats with unsaturated fats is associated with a reduction in cardiovascular outcomes in randomized trials and systematic reviews. Regarding sports, particularly endurance disciplines, aerobic metabolism makes extensive use of endogenous fatty acids (adipose and intramuscular) to sustain very long efforts; effectiveness depends on intensity, training, nutritional timing, and diet composition. Some omega-3 supplements show conflicting results for clinical events, while pharmacological doses of pure EPA have reduced events in selected populations. Limitations of the evidence include heterogeneity of studies, differences between foods and isolated nutrients, and the need to contextualize recommendations based on age, health status, and athletic goals.

Essential biological functions of fats

Lipids play central functional and structural roles in the body. They are fundamental components of the cell membrane, determining its fluidity and permeability; they participate in the synthesis of signaling molecules (e.g., prostaglandins and steroid hormones) and constitute stable energy reserves in adipose tissue. Vitamins A, D, E, and K require a lipid matrix to be absorbed and transported in the body; therefore, the presence of fat in the meal facilitates the bioavailability of fat-soluble nutrients. In the intestinal environment, microbial products such as butyrate also represent energy sources for colonocytes and participate in the metabolic and immune regulation of the mucosa; this illustrates that some molecules linked to lipids and carbohydrate fermentation contribute to intestinal health. Overall, the functions of fats encompass energy metabolism, vitamin integration, barrier function, and hormonal signaling: their presence in the diet is therefore necessary, not optional.

Fats and cardiovascular risk: evidence and interpretations

Modern research evaluates not only the quantity but also the quality of fats. Clinical trials and reviews indicate that reducing the saturated fatty acid content in the diet, when replaced with unsaturated fats (mono- or polyunsaturated), is associated with a reduction in cardiovascular events in randomized studies and meta-analyses [1][4]. Studies on dietary patterns rich in unsaturated fats, such as the Mediterranean diet enriched with extra virgin olive oil or nuts, have shown concrete reductions in cardiovascular events in controlled clinical trials [1]. Meta-analyses and systematic reviews support the idea that dietary choices and nutrient substitution are important determinants: avoiding trans fats and limiting saturated fats while prioritizing foods rich in mono- and polyunsaturated fats contributes to a more favorable risk profile [3][4]. Areas of debate remain — for example, the net effect of omega-3 supplements on global mortality varies between studies — and positive results are often associated with specific formulations, doses, and populations [5][6].

Fats and athletic performance: their role in endurance disciplines

In endurance sports (long-distance running, cycling, triathlon), aerobic metabolism uses both carbohydrates and fats; the proportion of energy derived from lipids increases with duration and at moderate intensities, while at high intensities, carbohydrates prevail. The ability to oxidize fats is influenced by training, sex, fitness level, and dietary habits: endurance training increases mitochondrial capacity and the ability to use fatty acids as fuel, delaying the depletion of glycogen stores [7]. Nutritional strategies that temporarily alter macronutrient availability (e.g., higher-fat diets) can increase lipid oxidation during submaximal exercise, but the effect on competitive performance is variable and sometimes counterproductive if it compromises high intensities. Professional guidelines suggest personalized planning of energy intake and macronutrients: the frequently recommended fat intake for athletes is in a moderate range, evaluating body composition goals, recovery, and dietary energy density [9].

Key mechanisms: how the body uses fats in exercise

Lipid oxidation requires the release of fatty acids from adipose tissue or intramuscular reserves, their transport to the muscle, and entry into mitochondria for β-oxidation. The point of maximal lipid oxidation (Fatmax) is typically observed at moderate intensities (~40–65% VO2max) and varies between individuals according to training and body composition [7]. As intensity increases, the energy contribution from fats decreases due to limitations in mobilization and oxidation; for this reason, during high-intensity efforts, carbohydrates remain critical for performance.

Quality and sources of fats: what to prioritize

Not all fats have the same biological profile. Modern dietary guidelines recommend prioritizing foods rich in monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), especially long-chain omega-3s, and limiting industrial trans fats. Recommended sources include extra virgin olive oil, oily fish, unsalted nuts, and seeds; these foods are associated with favorable biomarkers and reductions in events in observational studies and dietary pattern trials [1][3][13]. In the Mediterranean context, extra virgin olive oil and nuts are components that contribute to the benefits observed in randomized trials [1]. However, some saturated fats perform biological functions (e.g., structural components or local metabolites), and evaluation must therefore consider the overall dietary pattern and food type rather than demonizing individual nutrients.

Extra virgin olive oil

Extra virgin olive oil is a rich source of MUFA and phenolic compounds; studies on dietary patterns that include it show improvements in cardiovascular risk factors and a reduction in events in controlled clinical studies [1][3]. The effects appear to be related to both the lipid profile and the anti-inflammatory and antioxidant properties of the minor compounds present in the oil.

Oily fish and omega-3

Oily fish are dietary sources of EPA and DHA. Clinical evidence on omega-3 capsules is heterogeneous: some meta-analyses show modest or no effects on global outcomes, while trials with high doses or specific formulations (e.g., icosapent ethyl) have documented reductions in cardiovascular events in selected populations [5][6]. The dietary choice (eating fish 1–2 times/week) remains a prudent recommendation for general health.

Nuts, seeds, and vegetable fats

Regular consumption of nuts and seeds is associated with better lipid profiles and lower cardiovascular risk in prospective studies and meta-analyses. Adding moderate portions of unsaturated nuts to the diet is a practical strategy to increase PUFA and MUFA intake without excessively increasing carbohydrates or saturated fats [2][13].

Saturated fats and trans fats

Industrial trans fats are clearly harmful and their consumption should be avoided. For saturated fats, the literature suggests that the risk largely depends on what replaces them in the diet: replacing them with PUFA or MUFA tends to reduce cardiovascular risk, while replacing them with refined carbohydrates may not offer advantages [4].

What this means in practice

For endurance athletes and the general public, some practical indications emerge from the evidence: prioritize food sources of unsaturated fats (extra virgin olive oil, oily fish, nuts, seeds), reduce or avoid trans fats, and limit saturated fats by replacing them with unsaturated fats when possible. In athletes, the energy provided by fats supports prolonged activity and can help preserve glycogen stores; however, the balance between carbohydrates and fats must be adapted to training intensity and phases (training vs. pre-competition) to ensure optimal performance and recovery [9][7]. Incorporating foods rich in unsaturated fats into meals (for example, adding extra virgin olive oil to vegetables, nuts as a snack, fish in post-workout dinners) promotes the absorption of fat-soluble vitamins and improves the energy density of the diet without resorting to processed products. The use of supplements (omega-3, special fatty acids) should be evaluated on a case-by-case basis and based on clinical evidence, dosage, and individual profiling; not all formulations yield the same results [6][5].

KEY POINTS TO REMEMBER

• Fats are essential nutrients with structural, energetic, and regulatory roles.
• The quality of fats (unsaturated vs. trans/saturated) has greater clinical relevance than quantity alone.
• In endurance sports, fats provide important energy for prolonged efforts; the contribution depends on intensity, training, and diet.
• Dietary patterns such as the Mediterranean diet (extra virgin olive oil + nuts + fish) show cardiovascular benefits in randomized trials [1].
• Nutritional interventions and supplementation should be evaluated individually and with attention to available evidence.

Limitations of the evidence

It is important to distinguish between observational associations and causal evidence obtained from clinical trials. Observational studies can show useful correlations but are subject to confounding (lifestyle, overall dietary patterns). Meta-analyses and Cochrane reviews studying the reduction of saturated fats show benefits when these are replaced with unsaturated fats, but many trials have heterogeneity in intervention, duration, and population [4]. For omega-3 supplements, results vary depending on the formulation, dose, and population studied; trials with high-dose EPA have found different results compared to meta-analyses that include many variable formulations [5][6]. Relevant methodological limitations include imperfect dietary measures, short duration of some trials compared to the latency of chronic diseases, and variability in the composition of the foods studied. For athletes, most knowledge about metabolism comes from laboratory studies and small performance trials; long-term controlled studies are needed to define net effects on real competitive performance.

Editorial conclusion

Fats are not "enemies": they represent a necessary dietary component with essential biological roles and are fundamental energy resources in endurance activities. The choice of lipid sources and the overall quality of the diet determine the effects on health. For the general public and athletes, the practical approach is to prioritize unsaturated fats from real foods (extra virgin olive oil, fish, nuts, seeds), limit trans fats, and moderate saturated fats by replacing them with unsaturated fats when appropriate. Recommendations must be personalized: age, health status, athletic goals, and dietary preferences require a contextualized nutritional plan. Finally, interpreting the literature requires caution: replacing nutrients and comparing dietary patterns is often more informative than focusing on single compounds.

Editorial note

Article originally published in the past and updated according to scientific review criteria and communicative clarity. The text is for informational purposes only and does not replace personalized clinical advice; for medical or nutritional decisions, consult qualified professionals.

SCIENTIFIC RESEARCH

Selected list of studies and reviews cited in the text (order of citation). DOIs are provided for verifiability.

1. Estruch R, Ros E, Salas‑Salvadó J, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013;368(14):1279‑1290. https://doi.org/10.1056/NEJMoa1200303
2. Aune D, Keum N, Giovannucci E, et al. Nut consumption and risk of cardiovascular disease, total cancer, and all‑cause and cause‑specific mortality: a systematic review and dose‑response meta‑analysis of prospective studies. BMC Med. 2016;14:207. https://doi.org/10.1186/s12916-016-0730-3
3. Guasch‑Ferré M, Bullo M, Babio N, et al. Olive oil consumption and risk of CHD and/or stroke: a meta‑analysis of case‑control, cohort and intervention studies. Br J Nutr. 2014;112(2):248‑259. https://doi.org/10.1017/S0007114514000713
4. Hooper L, Martin N, Abdelhamid A, et al. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2020;8:CD011737. https://doi.org/10.1002/14651858.CD011737.pub3
5. Bhatt DL, Steg PG, Miller M, et al.; REDUCE‑IT Investigators. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia. N Engl J Med. 2019;380:11‑22. https://doi.org/10.1056/NEJMoa1812792
6. Ruscica M, Botta M, Magni P, et al. Omega‑3 polyunsaturated fatty acids supplementation and cardiovascular outcomes: do formulation, dosage, and baseline cardiovascular risk matter? Meta‑analysis. Pharmacol Res. 2020;160:105060. https://doi.org/10.1016/j.phrs.2020.105060
7. Maunder E, Plews DJ, Kilding AE. Contextualising Maximal Fat Oxidation During Exercise: Determinants and Normative Values. Front Physiol. 2018;9:599. https://doi.org/10.3389/fphys.2018.00599
8. Donohoe DR, Garge N, Zhang X, et al. The microbiome and butyrate regulate energy metabolism and autophagy in the mammalian colon. Cell Metab. 2011;13(5):517‑526. https://doi.org/10.1016/j.cmet.2011.02.018
9. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501‑528. https://doi.org/10.1016/j.jand.2015.12.006