Dietary choices are implicated in increasing risk, but sometimes it is hard to know where to look when seeking advice on what to eat!
But is it fat or sugar we should be more concerned about? Or both? It seems the answer to that question is a little complex.
First, let’s look at the action of insulin.
When insulin gets high
Insulin impacts the synthesis and storage of glucose, fat and amino acids. It is primarily recognised for its regulation of blood glucose levels, and maintains balance of levels of sugar in the blood by:
- moving glucose from the blood into muscle cells or adipose (fat) tissue, and;
- inhibiting the formation of glucose from non-carbs, i.e. fats and proteins (a process called gluconeogenesis that takes place in the liver when blood glucose runs low).1
It then gathers excess glucose in the blood and stores it as fat.
It also acts as an appetite regulator, and whilst its role is not well defined, once insulin acts to deposits fat into fat cells, leptin – the hunger suppressant hormone – is stimulated to release.1
In insulin resistance, it has been observed that glucose and free fatty acids are persistently high in the blood, likely due to ‘resistant’ cells not heeding to insulin’s call, meaning less glucose uptake by muscle cells, and adipose cells no longer inhibiting free fatty acid release.1
This then results in higher levels of insulin being produced, and chronically high insulin is known as hyperinsulinemia. Liver and kidney cells do not become resistant to insulin-like the muscle and fat cells, and instead are hyper-stimulated to produce triglycerides and retain sodium respectively. This results in high levels of TGL in the blood, and high blood pressure.1 Neither situation is great, especially for your heart.
So, considering insulin is involved in glucose and fatty acid storage and synthesis, will dietary intake of sugars or fats impact insulin activity?
Chronically, high intake of sugar and refined carbohydrates can contribute to insulin resistance.2 This is following the endless barrage from insulin requesting cells to take glucose from the blood, as mentioned above. Levels of both insulin and glucose can remain high, and eventually, the poor beta-cells of the pancreas may produce less insulin over time.1
However, eating carbohydrates from whole food sources, like veg, fruit, and whole grains or pseudo-grains like quinoa or buckwheat have less of an impact. The fibre in these guys slows the absorption of glucose into the blood, easing the pressure on the insulin being produced to deal with a massive hit of glucose.
So what about fat in the insulin resistance picture?
The impact of dietary fat on insulin production is a little more complex than that of is sugary cousin!
A very small portion of a fatty acid molecule can be used as glucose – but not enough to really impact blood glucose levels alone.
However, it has been found that a diet high in meat, specifically processed red meat, is associated with insulin resistance. And it is thought this may be due to the type of fat, rather than the protein content.3;4
It is thought the negative effects associated with high intakes of saturated fats from processed and red meat can become toxic, causing inflammation and oxidative stress in human adipose (fat) tissue, leading to impairment of mitochondrial function and insulin signalling, and consequently insulin resistance.4;5
In addition, the inflammatory response from high intake of processed and red meat may be made worse when the individual is overweight or obese.3
The high intake of saturated fatty acid palmitate, found in meat, dairy and eggs, has been connected to insulin resistance; whereas high intake of unsaturated fats from fish reduces the risk, and the monounsaturated fatty acid oleate (found in nuts, olive and avocado) actually increases insulin sensitivity, compared with high saturated fat and high-carb diets.3;6
It has also been found (in a small study) that a diet high in plant foods results in increased insulin sensitivity.7 Guess that is yet another tick for the Mediterranean diet!
However, we must remember that regardless of whether you eat meat, dairy and eggs or not, if your diet is high in processed foods this is going to be worse for health outcomes than eating some lean meat, dairy and eggs balanced with a heap of veg.
But this is understandable, right? Anything in excess, especially processed foods, really isn’t good for us.
What to do?
So, fat vs sugar in the war on insulin resistance – who wins? Well, it depends on the type of fat, and how you are eating your sugar (or carbohydrate).
Remember, every person is unique and responds differently to what they consume. If you have concerns, please consult with your healthcare practitioner for individualised dietary suggestions.
Overall, it seems the excessive consumption of highly processed fats and sugars, typical of a Western diet, are what to watch out for. So avoid heavily processed and refined versions of food including sugars, grains, meats, and oils.
Eat real, whole foods, as close to their original form as possible, prepared in a way that serves to nourish you.
Find balance on your plate, and eat in moderation. Consume healthy fats, found in oily fish, nuts, seeds, avocados and olives, and an abundance of anti-inflammatory foods, such as vegetables, herbs and spices. These foods can be protective and even increase insulin sensitivity. They provide kick-ass anti-inflammatory and antioxidant nutrients that can help mitigate and balance out the inflammatory nature of meat and saturated fat.
And remember that not all fats and carbohydrates are created equal.
By Angela Johnson (BHSc Nut. Med.)
- Gropper, SS & Smith, JL 2013, Advanced Nutrition and Human Metabolism, 6th, Wadsworth, Cengage Learning, Belmont CA
- Harvard School of Public Health 2016, Carbohydrates and Blood Sugar, viewed 30 June 2016, <https://www.hsph.harvard.edu/nutritionsource/carbohydrates/carbohydrates-and-blood-sugar/>
- Evans, WJ 2013, ‘Oxygen-carrying proteins in meat and risk of diabetes mellitus’, JAMA Internal Medicine, vol. 173, no. 14, pp. 1335-1336.
- Rachek, LI 2014, ‘Chapter Eight: Free Fatty Acids and Skeletal Muscle Insulin Resistance’, Progress in Molecular Biology and Translational Science, vol. 121, no. Glucose Homeostasis and the Pathogenesis of Diabetes Mellitus, pp. 267-292.
- Estadella, D, da Penha Oller do Nascimento, CM, Oyama, LM, Ribeiro, EB, Dâmaso, AR, & de Piano, A 2013, ‘Lipotoxicity: effects of dietary saturated and transfatty acids’, Mediators Of Inflammation, vol. 2013, p. 137579.
- Paniagua, JA, Gallego de la Sacristana, A, Romero, I, Vidal-Puig, A, Latre, JM, Sanchez, E, Perez-Martinez, P, Lopez-Miranda, J, & Perez-Jimenez, F 2007, ‘Monounsaturated fat-rich diet prevents central body fat distribution and decreases postprandial adiponectin expression induced by a carbohydrate-rich diet in insulin-resistant subjects’, Diabetes Care, vol. 30, no. 7, pp. 1717-1723.
- Gojda, J, Patková, J, Jaček, M, Potočková, J, Trnka, J, Kraml, P, & Anděl, M 2013, ‘Higher insulin sensitivity in vegans is not associated with higher mitochondrial density’, European Journal of Clinical Nutrition, vol. 67, no. 12, pp. 1310-1315.