Keto Diet: Any Impact On Blood Work?

The ketogenic diet is a popular weight-loss strategy that involves drastically reducing carbohydrate intake and replacing it with fat. While the keto diet has been shown to be effective for weight loss and has other health benefits, it can also have some adverse effects on your body, and it is easy to do it wrong. Therefore, it is important to regularly monitor what is happening inside your body with blood tests to ensure your 'healthy' diet is not having the opposite effect. Blood tests can show changes in your blood sugar, insulin, and cholesterol levels, as well as your thyroid function. These tests can help to identify potential issues such as insulin resistance, high cholesterol, and thyroid problems, which could increase your risk of developing conditions like type 2 diabetes, heart disease, and stroke.

Blood sugar levels

However, even if you don't have diabetes, it is recommended to monitor your blood sugar and insulin levels when following a keto diet. This is because there is evidence to suggest that the keto diet may affect the body's ability to respond to insulin, a condition known as insulin resistance. Insulin resistance can increase the risk of developing type 2 diabetes and cardiovascular disease.

When on a keto diet, it is common to experience a "dawn phenomenon", where blood sugar levels are higher in the morning as the muscles are in "glucose refusal mode". This is not usually a cause for concern, as blood sugar levels tend to remain low throughout the rest of the day.

It is also worth noting that standard reference ranges for blood sugar levels are based on a high-carb diet. Therefore, it is expected that people on a keto diet will have lower blood sugar levels, typically between 3.0 to 3.9 mmol/L or 54 to 70 mg/dL after following a low-carb diet for several months.

In summary, monitoring blood sugar levels is crucial when following a keto diet to ensure that your body is responding well to the dietary changes and to mitigate any potential risks associated with insulin resistance.

Insulin resistance

Skeletal Muscle

Skeletal muscle is the main tissue responsible for glucose disposal (about 70%) after a caloric load. However, when the needs for skeletal muscle glucose uptake exceed its capacity, the excess glucose moves to the liver, causing de novo lipogenesis. The increased flux of fatty acids and the metabolic overload in muscle cause an increase in intramuscular diacylglycerols, long-chain acyl CoAs, ceramides, and triglycerides. The intramuscular levels of these molecules are positively correlated with muscle triglyceride content and negatively with insulin sensitivity.

Liver

The metabolic overload and the increased lipids flux increase the concentration of diacylglycerols, long-chain acyl CoAs, ceramides, and triglycerides mainly through the increased level of malonyl CoA, which serves as a precursor for de novo lipogenesis but also as the inhibitor of carnitine palmitoyl transferase-1, which is fundamental for the entry of long-chain acyl CoAs into the mitochondria for beta-oxidation. Moreover, the inhibition of the expression of beta-oxidative enzymes in the liver induced by the effect of insulin on PGC1α facilitates the increase in ectopic fat in the liver, leading to insulin resistance.

Adipose Tissue

A normal quality/quantity of white adipose tissue is fundamental for the normal regulation of insulin action. On the other hand, the impaired antilipolytic effect of insulin on adipose tissue increases the efflux of circulating free fatty acids that, in turn, act on skeletal muscle and liver. Moreover, the increase in adipose tissue (mainly visceral adipose tissue) creates an inflammatory milieu that worsens local, liver, and muscle insulin sensitivity.

Metabolic Inflexibility

Direct Effects of Weight Loss on Insulin Sensitivity

Although not all individuals with obesity are insulin-resistant, there is a well-demonstrated connection between these two phenomena, which is largely attributed to adipose and other tissues' metabolic dysfunctions. The hormonal milieu facilitating insulin resistance within the adipose tissue is worthy of more substantial discussion. Indeed, adipocytes secrete several hormones (adipokines) that can act on glucose and lipid metabolism as well as both anti-inflammatory or inflammatory mediators.

Direct Effects of Ketogenic Diets on Insulin Sensitivity

The effect of ketogenic diets on insulin sensitivity appears to be mediated by other factors than the weight loss itself. The restriction in carbohydrate intake decreases intestinal absorption of monosaccharides, leading to reduced postprandial glycemia, decreased insulin requirements from the pancreas, and lower insulin levels and insulin-to-glucagon ratio. For example, the insulin required to metabolise a ketogenic meal is almost ten times less than that necessary to metabolise a Mediterranean diet meal.

The effectiveness of the ketogenic diet in lowering fasting blood glucose was confirmed in a recent meta-analysis including type 2 diabetes patients, which showed a decrease of about 1.29 mmol/L in fasting blood glucose and 1.07 in glycated haemoglobin. The ketogenic diet also improved lipid metabolism, with significant reductions in triglycerides and total cholesterol and significant increases in HDL-c. Notably, the therapeutic effects of the ketogenic diet occurred despite the duration of the intervention, which ranged from 1 to 56 weeks.

Another recent meta-analysis comparing the effects of 3, 6, and 12 months of ketogenic diets with any diet recommended for patients with type 2 diabetes showed that 3 and 6 months of a ketogenic diet produced a more significant reduction in glycated haemoglobin, body weight, and triglycerides and a greater increase in HDL-c compared to the other diets, with no differences in LDL-c between groups. After 12 months, dietary differences between glycated haemoglobin and weight loss disappeared, but the triglycerides remained significantly lower in the ketogenic diet group while LDL-c reductions were more pronounced in the control diet group.

In summary, ketogenic diets improve insulin sensitivity through their irrefutable effects on fat and weight loss. Besides weight loss, ketogenic diets produce direct insulin-sensitising effects, which are mostly due to the capacity of their restricted-digestible carbohydrates content to lower blood glucose and insulin levels. In addition, ketone bodies appear to be able to influence insulin signalling directly. Despite the promising role of ketogenic diets on type 2 diabetes prevention, future studies should address their long-term efficacy and safety in diabetic individuals.

Cholesterol levels

The keto diet is a popular, strict, low-carb, high-fat, and moderate-protein diet. It involves restricting your total carbohydrate intake to 20–50 grams per day, which forces your body to shift from using glucose as its main source of energy to using ketone bodies, a type of chemical formed from the breakdown of fat.

The keto diet may affect cholesterol levels, but more research is needed to draw precise conclusions. Cholesterol levels are linked to heart disease risk, so it is important to discuss this diet with a healthcare professional before trying it, especially if you have other risk factors.

How Keto Affects Cholesterol

There has been some research on low-carbohydrate diets and their effects on cardiovascular health. However, it is challenging to draw definitive conclusions, as many studies are older, short-term, have a small sample size, or examine different variations of very low-carb diets.

Some studies suggest that the keto diet can lower levels of high-density lipoprotein (HDL), or "good", cholesterol but raise levels of low-density lipoprotein (LDL), or "bad", cholesterol. For this reason, the keto diet may not be appropriate for everyone, especially those with high cholesterol.

Predicting How Keto May Affect Your Cholesterol Levels

To determine whether the keto diet may negatively impact your cholesterol, consider your starting triglyceride number. According to the Mayo Clinic, normal levels are less than 150 milligrams per decilitre (mg/dL). If you have normal levels, keto is likely safe to try, as the impact from keto is expected to be minimal or non-existent.

On the other hand, if you have insulin resistance, type 2 diabetes, and/or abdominal obesity, and your triglycerides are elevated, keto may help decrease insulin resistance and improve triglycerides. Research supports this, as a small study published in 2020 in Nutrition & Metabolism found that those on a very low-carb diet lost three times the visceral fat compared to the low-fat group, with improvements in insulin sensitivity, triglyceride levels, and HDL cholesterol.

How to Follow Keto in a Heart-Healthy Way

One of the appeals of the keto diet is the idea that you can eat any and all fats. However, this is not a healthy mindset. Cardiologists recommend choosing cardioprotective (unsaturated) fats, like nuts, nut butter, seeds, avocado, and extra virgin oils such as olive oil. Similarly, it is important to avoid foods high in saturated fat, like butter, as your primary fat sources.

It is also crucial to maximise the small number of carbohydrates allowed. Getting enough fibre can be challenging on the keto diet, so it is important to ensure you are eating plenty of low GI-index veggies (non-starchy choices such as spinach and broccoli). Ultimately, the benefits come from replacing processed carbs, which are detrimental to overall wellness, with heart-healthy, unsaturated fats.

The Bottom Line

The keto diet alone may not contribute to the cholesterol spike that some people report when starting the diet. However, if you start eating more saturated fat because you are on keto, your LDL cholesterol will likely rise. An increase in saturated fat intake has been repeatedly shown to increase LDL.

Keto may also be dangerous for people with a genetic mutation that affects LDL regulation. If these individuals follow a keto diet, their LDL levels can skyrocket. This result is not common enough to skew overall results in population studies, but what matters most is the effect the diet has on individual health.

If you are considering adopting the keto diet, it is important to talk to your doctor first and incorporate only heart-healthy fats into your diet.

Thyroid hormones

The thyroid gland produces two primary hormones, triiodothyronine (T3) and thyroxine (T4). T3 is the more biologically active form, and T4 is converted into T3 in the liver, kidneys, brain, and gut through a process called deiodination.

The keto diet is a high-fat, low-carbohydrate diet. It can be beneficial for people with epilepsy or insulin sensitivity. However, it is not typically recommended for people with hypothyroidism, as it may decrease thyroid hormone production.

• Decreased Thyroid Hormone Production: The keto diet restricts carbohydrate intake to less than 20-50 grams per day. Carbohydrates are broken down into glucose, which is essential for producing thyroid hormones. When carb intake is reduced, the conversion of T4 to T3 declines, leading to decreased levels of the active thyroid hormone T3.
• Increased Inflammation: Prolonged ketosis can force the body to accumulate acid, which may encourage inflammation. People with thyroid diseases often suffer from chronic inflammation, especially in Hashimoto's disease and Grave's disease.
• Micronutrient Deficiencies: The keto diet may lead to deficiencies in micronutrients such as potassium and vitamin C, which are essential for overall health and thyroid function.
• Elevated Cortisol Levels: The keto diet may increase cortisol levels, which can further decrease thyroid function. Cortisol is a stress hormone that can suppress the hypothalamic-pituitary-adrenal (HPA) axis and decrease the production of thyroid hormones.

While the keto diet may have some benefits, it is important to consider its potential impact on thyroid hormones, especially for individuals with hypothyroidism. It is always recommended to consult with a healthcare professional before starting any new diet, especially if you have a medical condition.

Inflammation markers

The keto diet can have a significant impact on inflammation markers in the body. Inflammation is a natural process that helps the body heal and protect itself from illness and other damage. However, chronic inflammation can lead to serious health issues.

The keto diet is anti-inflammatory and can help manage and reduce inflammation symptoms. This is because the keto diet is very low in sugar, which helps prevent surges of insulin caused by unregulated blood sugar levels, a common trigger of inflammation in the body.

In addition, ketosis, the metabolic state that occurs when following the keto diet, releases ketones, which are powerful anti-inflammatory agents. One particular ketone, beta-hydroxybutyrate, has been found to block the NLRP3 inflammasome, an immune system receptor linked to inflammation.

Research has shown that the keto diet can reduce inflammation markers in the body. One study found that a long-term ketogenic diet resulted in a reduction of triglycerides and LDL-cholesterol, both of which are linked to an increased risk of heart disease when present in high levels.

Furthermore, the weight loss often associated with the keto diet can also lead to a reduction in inflammation markers. This is because fat cells, particularly visceral fat, can produce inflammatory molecules. Therefore, losing weight and reducing body fat through the keto diet can help lower inflammation.

Overall, the keto diet has been found to have anti-inflammatory effects, which can be beneficial for managing and reducing inflammation-related symptoms and conditions.

Frequently asked questions