Ask the Doctor: ‘Is a Keto diet safe, or could it raise my cholesterol?’

“I am trying to lose weight, approximately four stone and have been researching diets to help me do this. I would rather not take drugs such as Ozempic if I can do it myself. One I see come up continually as being successful is the Keto diet. I have no heart problems; my cholesterol is a little high but not high enough to be on medications. Is this safe for my heart or could it cause problems, or further raise cholesterol?”

Answer from Professor Robert Kelly MD MBA FRCPI, Consultant Cardiology & Lifestyle Medicine, Beacon Hospital, Dublin

I must congratulate you for your goal to lose weight and your preparedness to do something meaningful and safe to achieve this.

The most effective way to successful long term weight loss is by taking small steps of lowering weight by two or three pounds each week. A goal of four stone is great, but you need to break it down to smaller goals and build up the progress slowly over time. In your case this big goal can be achieved over 16-24 weeks, by following proven steps below.

There are several ways to reduce your weight by changing your food intake, lowering calories, and increasing physical activity.

The Keto diet is a highly effective way to lose weight and lower blood sugar, which will also calm food cravings. It is a low carbohydrate, high fat diet (typically 70-80% fat, 10% carbohydrate and 10-20% protein). Most people derive energy from carbohydrates. In the Keto diet that energy is instead derived from fat breakdown. This is more efficient and leads to weight reduction and, lower appetite. However consuming substantial amounts of fat may increase cholesterol levels especially when the fat is sourced from animals and ultra-processed food sources (packets, processed foods).

The diet consists of full fat dairy, meats, cheeses, fish, eggs, plant oils, avocado, low carbohydrates, and green vegetables. You must eat the vegetables and not stop. Doing that will deprive you of vital minerals and nutrients that your body needs to work and it may trigger heart arrhythmias like atrial fibrillation.

Keto is useful as a short-term solution for losing weight – up to 6 months but not as a long-term option.

In your case where the cholesterol is raised you might get initial benefits with Keto. Your cholesterol is made from Triglycerides, HDL, and LDL fragments. The latter is bad cholesterol that can lead to heart attack / stroke. Keto diet can lower triglycerides, but it can elevate LDL. You could adjust the macros (carbohydrate, fat, and proteins and /or switch animal fat to plant sourced fats as a potentially healthier option – so called Ketotarian diet).

As the diet disrupts cholesterol and lowers blood sugar, it is not advised to use it if you are taking diabetes medicines like Ozempic without talking to your doctor. If you have exceedingly high triglycerides, previous pancreatitis, genetically high cholesterol, liver failure or are pregnant you should not go on the Keto diet.

The Keto diet can give unpleasant short term side effects including “Keto-flu” feeling flu-like symptoms as your body gets used to fat based Ketosis instead of sugar. You may feel constipated, nausea, fatigue, reduced exercise tolerance and bad breath. It is also dehydrating, so drink gallons of water each day.

In your case I would suggest the following options:

1. Consider a Ketotarian diet with plant-based fats. Watch your cholesterol while on the diet.
2. Try a balanced diet such as Mediterranean or Whole Food Plant based diets. These are the two best for your health, lowering cholesterol, reducing heart disease, cancer, and Alzheimer’s disease risk. You can lose weight with these diets by eating less sugar, consuming less alcohol, eating smaller portion sizes and more vegetables, and drinking more water will curtail appetite. Limit ultra processed foods which can give you heart problems, cancer, and weight gain.
3. Any of these three options will work in your case. Your goal should be two pounds of weight loss per week. You can start with one pound if it is easier. You will need to take exercise (brisk walk) each day and spend time with family for meals really helps too. This is how I help my patients to improve their heart health (lifestyle medicine), by taking incremental small steps each day that lead to significant reductions in weight over a few months. Remember that sustaining these changes with time make it more likely for you to keep to this new health habit.

Have a question for the professionals you’d like answered? Get in touch with sarah.gill@image.ie with the subject headline ‘Ask The Doctor’.