Athletes and strength: is it time to love fat?

It’s a widely-held belief that athletes seeking maximum performance should stick to low-fat diets. But as Sports Performance Bulletin explains, this view may be over-simplified, especially when it comes for those whose events demand high levels of strength and power

Scan the ingredients list of any tub of ‘strength/weight gain’ protein powder and it’s easy to see the default thinking on sports nutrition and strength building. While the brands may differ, the contents are strikingly similar; all are invariably high in protein, low in fat, with varying amounts of carbohydrate. The reasoning is simple. Dietary protein provides the source of amino acid building blocks needed by your body to synthesise new muscle tissue, as well as to replace and repair tissue broken down during exercise itself.

Although the exact protein requirement for athletes remains the subject of debate, the consensus among sports nutritionists is that athletes do need more protein for optimum performance and recovery than their sedentary counterparts. In fact a large body of research suggests that athletes engaged in intense training actually need to ingest about 1.5-2.0 times the normal RDA for protein in order to maintain a positive protein balance(1-4). This equates to 105-140g of protein per day for a 70kg athlete. [For a more detailed discussion on protein requirements, see this article and also panel 1 below]

Panel 1: Recent thinking on protein intake

Although the optimum protein intake for athletes might seem like ‘settled science’, recent research continues to throw up new findings. For example, in a comprehensive review study (a study that pools findings from a number of previous studies on the same topic) on this topic, researchers reviewed all of the evidence to date on optimum protein intake amounts for athletes seeking maximum performance. They concluded the following:

  • #Regarding the 1.5-2.0g/kg/day range for athletes, strength and power athletes are recommended to consume protein intakes near to the top of this range; while endurance athletes might need slightly lower amounts.
  • #Relating to above however is that temporary ingestion of higher quantities during intense periods of training may provide additional benefit.
  • #Because muscle protein synthesis is upregulated for 24 hours following exercise and the body is primed to absorb more protein during this period, this is an ideal time to optimize protein intake in order to maintain muscle mass after endurance exercise (especially as prolonged endurance exercise may induce a catabolic state and muscle breakdown).
  • #Athletes should ingest 0.25-0.3g/kg (around 20-25g in total) of a quality protein source such as whey in the immediate period after exercise, and certainly no later than two hours post exercise. This practice will maximally stimulate signalling proteins known to stimulate muscle growth and recovery.

An historical perspective

Fifty years ago, high protein steak and egg diets were the order of today. The thinking was simple: ‘Muscles are made of protein; therefore to develop muscular strength requires a large intake of protein’. However, as the understanding of carbohydrate metabolism and sports performance grew, scientists began to realise that this approach was grossly oversimplified. That’s because we now know that the uptake of amino acids into muscle cells is strongly regulated by hormones.

One of the most anabolic (ie muscle building) hormones in the body is insulin, which is released whenever carbohydrates are eaten The primary job of insulin is to regulate the amount of glucose in the blood that results from eating carbohydrate, by stimulating cells to take up glucose. However, this release of insulin also has a potent anabolic effect, helping to drive amino acids into muscle cells, thereby stimulating muscle protein synthesis.

But carbohydrates also play another valuable role in muscle metabolism – that of helping to conserve hard earned muscle tissue. While a high-protein diet provides plenty of amino acid building blocks to build muscle protein, unless there’s sufficient carbohydrate present to support training (remember, carbohydrate is the body’s ‘premium grade’ fuel for exercise), these amino acids are simply used to supplement the fuel supply. A low-carbohydrate diet combined with vigorous exercise therefore results in protein oxidation for energy, and since muscles are the major store of amino acids, this can result in muscle tissue loss, especially when training volumes are high.

Moreover, research has clearly demonstrated the importance of ample dietary carbohydrate in reducing the amount of catabolic stress hormones, such as cortisol and adrenaline, which are released during and after exercise and which stimulate the breakdown of muscle tissue (6-8). In short, carbohydrate is as much as part of the ‘anabolic equation’ as protein.

Given that both protein and carbohydrate are needed for muscle growth and maintenance, it’s easy to understand how the consensus that high protein/ample carbohydrate/low-fat diets are best for strength athletes has arisen. A diet containing moderate or high levels of fat and plenty of protein/carbohydrate would necessarily contain a lot of extra calories, especially as each gram of fat provides 9kcals of energy – double that of carbohydrate or protein. And as we know, an excessive calorie intake leads to gains in body fat – exactly what most athletes don’t want!

Meanwhile, a calorie-controlled moderate/high-fat diet would necessarily have to contain relatively little protein and carbohydrate – again not desirable for an athlete seeking to maintain or build strength. Together, these facts explain why protein is king, and why (notwithstanding the growing realisation of the importance of essential fatty acids – see this article) fat is almost seen as a dirty word among some strength athletes.

A fly in the high-protein, low-fat ointment?

Gaining and retaining muscle tissue certainly requires ample protein and carbohydrate, but that’s not the whole story. After all if it were, consuming larger and larger quantities of protein would lead to ever increasing strength and muscle size – something that obviously doesn’t happen. This is because hormones also control the metabolism of muscle tissue and protein turnover. Naturally occurring anabolic hormones such as testosterone and human growth hormone (HGH) act as chemical messengers, directing muscle cells to take up amino acids and synthesise muscle protein. They also stimulate the oxidation of fat for energy, thereby increasing lean muscle mass while decreasing fat mass. The action of anabolic hormones is balanced by other ‘catabolic’ hormones, such as adrenocorticotrophic homone and cortisol. These hormones are released during ‘fight or flight’ situations, where energy production becomes paramount, and tend to produce a breakdown of body tissue. Building or maintaining strength requires a hormonal balance that is more anabolic than catabolic.

Higher fat, more strength?

Can anabolic/catabolic hormonal balance be influenced by nutrition? Well, there is evidence that protein and fat ratios can impact on hormonal balance, but in a rather surprising way. A 2004 study examined the relationship between dietary intake patterns and the resulting blood concentrations of the anabolic hormones testosterone (T), free testosterone (FT), and growth hormone(9). In this study, eight strength athletes and ten physically active non-athletes were examined at rest as well as after heavy-resistance exercise. During the first part of the study, all the subjects were allowed to eat freely, but kept detailed food diaries. The scientists then examined how these differing dietary patterns affected the levels of hormones in each athlete. In the second part of the study, a sub-group of 5 strength athletes and 5 non-athletes kept diaries for a further 4 days before undertaking a high volume, high intensity resistance workout. The findings were surprising:

  • #During the non-active period, a higher fat intakes and lower protein intake was associated with increased levels of anabolic hormones across both groups of subjects.
  • #During the phase of the study containing the high-intensity resistance exercise, this correlation disappeared for the non-athletes, but remained for the trained strength athletes – ie higher fat intakes and lower protein intakes were associated with increased blood levels of anabolic hormones in the strength athletes only.

The clear implication is that the role of diet in producing a favourable anabolic environment may be more important for trained athletes.

Although surprising, these early findings gained support from later studies. In one of these studies, the interaction between fat metabolism and muscle-building growth hormone was examined(10). To do this, the subjects were fasted for 37 hours, in order to suppress their natural production of growth hormone (GH – suppression of growth hormone normally occurs during fasting). They were then infused with the following:

  • *GH alone
  • *GH together with a drug called Acipimox, which blocks the release of fat from fat stores and fat metabolism
  • *No GH with Acipimox
  • *GH with Acipimox, plus extra lipid (ie to provide the body with an extraneous source of fat)

The results were as follows:

  • #As expected, urinary urea excretion, blood urea and muscle protein breakdown (all are measures of protein breakdown in the body) were increased by almost 50% during the fast when fat metabolism was being suppressed.
  • #Giving extra GH alone reduced the rate of muscle loss during the fast, but when the subjects were also being infused with Acipimox, extra GH didn’t reduce the rate of muscle tissue loss.
  • #However, when fatty acids were then added to the infusion (to provide a source of fat), the rate of whole body protein degradation dropped to just 15% above baseline values (ie the GH was able to exert an effect again), providing strong evidence that fatty acids in the bloodstream are important protein-sparing agents during fasting.

The scientists concluded that fat seems to plays a decisive role in the process of protein conservation during fasting in humans, possibly by helping growth hormone to work more efficiently.

Meat and strength

Another fascinating study examined the effect of meat containing diets and vegetarian diets on strength body composition when combined with resistance training(11). In this 12-week study, nineteen men were split into 2 groups:

  • *Ten subjects were instructed to continue consuming their normal omnivorous diet (containing a mixture of protein sources including meat) while the resistance training was continued.
  • *The remaining nine men were counselled to select a lacto-ovo vegetarian diet (ie exclude all meat) for the duration of the study.

All of the subjects kept food diaries, and while carbohydrate, protein, nutrient and alcohol intakes were not significantly different between the two groups, those on the meat diet tended to consume more fat, especially saturated fat.

Once again, the results confounded the researchers. Although the 12-week resistance training program produced the same gains in maximal strength (10-38%) in both groups of men, the changes in body composition and skeletal muscle size were significantly different. The meat eaters gained an average of 1.7kgs of lean muscle, while the vegetarian group lost an average of 0.8kgs. Moreover, the meat group lost an average of 1.3kgs of fat, while the vegetarian group actually gained 0.1kg. Although the researchers cautioned that the food diary methods they employed could not be considered 100% accurate, they did conclude that there was a significant difference between the two dietary patterns.

Up to date

In a recent large retrospective study on dietary fat intake and testosterone levels in men, researchers examined dietary data gathered from previous studies to try and determine the strength of the association between fat intake and testosterone, and whether any other key nutrients were also implicated(12). There were seven key nutritional factors identified as being inversely associated with testosterone deficiency. These were:

  • Vitamin A
  • Protein intake
  • Total fat intake
  • Overall saturated fatty acid intake
  • Monounsaturated fatty acid intake (eg oleic acid as found in olive oil)
  • The intake of a particular saturated fatty acid (16:0,)
  • Intake of the mineral phosphorous

When the data was analysed further, the researchers concluded that low dietary fat was particularly associated, along with, low vitamin A and phosphorous/protein intakes.

Take-home message

Do these findings mean that sportsmen and women should abandon the currently accepted nutritional wisdom and switch to much high-fat diets with little regard to protein intake? Not at all! Firstly, we can see from the study above that too low a protein intake could be detrimental to creating an anabolic environment in the body. And it’s important also to understand that traditional high-fat diets associated with a sedentary lifestyle are NOT associated with better strength or performance. Indeed, a very recent study found that habitually high levels of dietary fat intake in older adults is associated with lower muscle strength and poorer functionality(13).

However, what the research does illustrate are the complexities of formulating optimum eating regimes for athletes – and the notion that a low-fat diet guarantees high performance. In particular, the data suggest that the practice among some athletes of following extremely low fat diets, or eschewing all red meat from the diet on the grounds that it contains more fat than other protein sources may actually be counterproductive. More research remains to be done, but in the meantime it seems that if you’re partial to some (less than perfectly lean) red meat now and again, a little of what you fancy really may do you some good! As a bonus, your intake of another key nutrient for performance – iron – will almost certainly be boosted – but that’s another story, and one which you can read about here!


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  2. J Appl Physiol 1988;64(1):187-93
  3. J Appl Physiol 1992;73(5):1986-95
  4. Curr Opin Clin Nutr Metab Care 1999;2(6):533-7
  5. J Clin. Invest. 95: 811–819, 1995
  6. Int J Sport Nutrition, 8, 49–59, 1998
  7. Journal of Applied Physiology, 84, 1917–1925, 1998
  8. International Journal of Sports Medicine, 22, 226–231, 2001
  9. Int J Sports Med. Nov;25(8):627-33, 2004
  10. J Clin Endocrinol Metab, 88(9): 4371-8, 2003
  11. Am J Clin Nutr, 70 (6), 1032-1039, 1999
  12. Hormones volume 19, pages205–214(2020)
  13. Clin Nutr. 2020 Mar 27;S0261-5614(20)30135-7

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