You can’t outrun a bad diet. At least, that’s been the perceived wisdom until now. But a new study by Aberdeen University suggests that without changing anything about what we eat – saturated fat and all – you can improve your health and lose weight.
The study shows that processes that occur in your heart and blood (your cardio-metabolic health) is the biggest driver in how our bodies use different fats as fuel. For eight weeks, the male athletes in the study swapped exercise regimes with sedentary males who had Type 2 diabetes. Researchers found that one hour of vigorous exercise a day enabled those with Type 2 diabetes to lose weight, improve insulin sensitivity, sugar control and lower their cholesterol.
The study demonstrated that athletes and people with Type 2 diabetes burn saturated fat differently and that the participants with Type 2 diabetes could reverse the difference (in weight, insulin sensitivity, sugar control and cholesterol) following an eight-week ‘lifestyle swap’.
Interestingly, neither cohorts changed anything about their diets, which were comparable in amount and quality. Not only does it challenge the perceived wisdom around the role of exercise in health, it also supports the idea that saturated fats aren’t as straight-forwardly harmful as previously thought; and might even be the preferred fuel for the very fit.
“It’s made me look at exercise differently,” says Prof Dana Dawson who led the research team. Regarding the role of saturated fat in health, she adds: “In a sense maybe they’re not so much the bad guys. It’s about how healthy our bodies are to utilise the saturated fat, rather than that they are a poison.”
Why do saturated fats have a bad rep?
In the past 60 years there has been a strongly held consensus that all fat was bad, especially saturated fat because it causes rises in LDL ‘bad’ cholesterol. Excess LDL cholesterol contributes to plaque buildup (atherosclerosis) in your arteries. “We have evidence that too much saturated fat can increase the risk of cardiovascular disease and raise the levels of LDL cholesterol in the body,” says the dietitian Priya Tew. “Swapping saturated fats for unsaturated fats can help with this.”
Our bodies do need saturated fats in small amounts because our cells are made of 30-40 per cent saturated fat and it provides essential structure for our bodies.
“They are needed for hormone production, cell membranes and for energy too,” says Tew. “Plus we have fat soluble vitamins.” Vitamins A, D, E, and K are absorbed and stored in our fat cells.
The recommendation is that men have no more than 30g saturated fat a day and women 20g. For reference, 100g of butter contains 51g of saturated fat, and 100g of pepperoni contains 15g saturated fat.
Saturated fat: The good and the bad
The fear around saturated fats led to very low-fat diets rising in popularity but these have subsequently been found to be detrimental to our overall health. “The diets were linked to vitamin deficiencies and even depression,” explains the dietitian Dr Carrie Ruxton.
The latest thinking is that saturated fat isn’t one thing and that there are 10 types of saturated fat or ‘fatty acids’. “These different types of fatty acids are needed in the diet in different proportions,” says Dr Ruxton.
For example, dairy fat contains a saturated fat called palmitic acid which scientists now think has a mostly neutral effect. “Even stearic acid, a fatty acid found in meat, appears to have a neutral effect on heart disease risk markers.”
Myristic acid (a type of saturated fat present in butter, milk, coconut and palm oils) and lauric acids (in similar foods plus nuts and seeds) seem to have the strongest association with increased blood lipid levels.
“It would be impossible to specifically avoid these fatty acids as most fat-containing foods contain a combination of fatty acids,” Dr Ruxton notes. And while some animal and plant fats (coconut, palm) contain a larger proportion of saturated fat, even plant foods like sunflower oil, nuts, seeds and avocados contain a mix of unsaturated and saturated fats. “So it would be almost impossible to exclude all saturated fats from our diets.”
Fat and exercise
The scientists behind the study at Aberdeen wanted to investigate what is known as the “athlete’s paradox”. “This is where athletes store higher levels of fats in their bodies and muscles,” explains Tew.
We know that endurance athletes train themselves to use fat as a key energy source for long distance runs or cycles. “This is because fat is a denser source of energy, and our bodies can store more of it compared with carbohydrates (which are stored in the liver and muscle as glycogen),” says Dr Ruxton.
Saturated fat: A secret weapon?
The researchers at Aberdeen University were curious as to how athletes can have a high amount of fat in their muscle cells, and yet be at the opposite spectrum of health and insulin sensitivity to people with Type 2 diabetes.
“You have two populations where if you look at their muscle, at face value they are similar, but really they are at opposing ends of cardiometabolic health,” says Prof Dawson. “Our thinking was that there has to be something that’s different about this fat.”
The study looked at what the storage pattern of saturated and unsaturated fats in the participants’ skeletal muscle was, as well as the ability of utilising saturated and unsaturated fats.
“We were quite surprised to find that athletes stored a lot more saturated fats in their skeletal muscles. And they were also using it at the peak of their ability to exercise when they were training intensely,” says Prof Dawson.
Whereas in patients with diabetes, who before the study did no more than 10 minutes of exercise a day, they had increased storages of unsaturated fat in their skeletal muscles. And their ability to utilise both unsaturated and saturated fat was much lower than the athletes.
The fat swap
The athletes in the study were male triathletes in their 50s training more than nine and a half hours a week of vigorous exercise. Over eight weeks the athletes were deconditioned and the diabetics took over their training routine which included one hour of cycling every day.
While the athletes didn’t change a lot because they were already very healthy, the patients with diabetes changed dramatically through that exercise.
“After eight weeks, their blood sugar control was better and their cholesterol was much lower. They became more insulin sensitive and their triglycerides lowered as well. And they completely changed the spectrum of storage of saturated and unsaturated fat in their skeletal muscle,” says Prof Dawson.
Though the scientists didn’t control diet, participants kept a food diary throughout the experiment which showed their intake was fairly constant and comparable. “We wanted to make sure that the people who were exercising for the first time didn’t change their diets drastically,” Prof Dawson adds.
After eight weeks the skeletal muscle of patients with Type 2 diabetes was indistinguishable from that of the deconditioned athletes. “We realigned their phenotypes in just eight weeks.”
How much exercise do you need to do?
The take home message is that you don’t have to be an elite athlete to encourage your body to burn fat. “In the study, just eight weeks was enough to turn around the unhealthy diabetic metabolism and promote fat burning through regular exercise,” says Dr Ruxton.
The study tells us that our ability to utilise saturated fat is directly proportional to your physical fitness. “That’s probably why athletes and regular exercisers can ‘get away’ with tolerating more fat in their diets – even saturated fats from meat and butter – because they have trained their bodies to use it as an efficient fuel source,” says Dr Ruxton.
Regular exercise switches the body to burn more fat by storing it next to the mitochondria (energy giving cells) in the muscles. “It’s a bit like having your coal right next to your furnace – and it’s more efficient,” Dr Ruxton explains. The study only looked at endurance exercise. “We weren’t quite savvy at that time to recommend for example a mix of endurance and resistance,” says Dr Dawson. “We now know a combination of the two is probably better.” So taking up 60 minutes of daily exercise that raises your heart rate will change how you store and burn saturated fats.
Is exercise or diet more important?
“It opens up the discussion really about the fact that it’s probably not the dietary advice that we need to focus on but the exercise advice,” says Dr Dawson.
Saturated fat is a useful energy source as it’s easily broken down during exercise, but only if you’re a regular exerciser. “The muscles in athletes are extremely reliant on saturated fat for performance. But only because their utilisation of saturated fat is directly proportional to their degree of health,” says Dr Dawson.
Given that 60 per cent of the adult population is overweight, unless you become committed to an active lifestyle, you shouldn’t hit the butter.
“Saturated fat can still have harmful effects on blood cholesterol levels and inflammation when we are sedentary and overweight,” says Dr Ruxton.
Also, not all saturated fats are the same. “Dairy foods and lean red meats are fine.” says Dr Ruxton. “Just ensure that most of the fat you eat is from plant sources so you get a mix of fatty acids; olive oil, nuts, seeds.”