Have you ever wondered what people actually mean when they talk about a high-fat diet?

You may have heard terms such as LCHF (Low-Carbohydrate, High-Fat) or Keto (Ketogenic).  Are these two ‘diets’ the same thing?  Not quite.

A high-fat diet simply means that a larger proportion of your daily calories comes from fat. There isn’t one universal definition of exactly how much fat makes a diet ‘high fat,’ because dietary patterns vary.

With an LCHF diet, carbohydrates are reduced, while fat generally, makes up a larger proportion of the diet.  However, instead of eating lots of fat, many people are eating a low carb way of eating, and are using more Protein, instead of a lot of fat. Protein fills you for longer, and, contains less calories than fat does.

A ketogenic diet takes carbohydrate restriction further, usually reducing carbohydrate intake enough, to encourage the body to enter into a metabolic state called ketosis (burning fat for energy, instead of glucose from carbohydrates).

Also, when we use the word ‘diet,’ we’re simply talking about the food someone eats, and not,  a short-term programme designed to restrict calories.

What Happens When We Reduce Carbohydrates?

Our bodies can use different sources of energy. When carbohydrate intake is substantially reduced, the body makes greater use of stored fat. During a ketogenic diet, the liver also produces ketones, which can be used as an alternative fuel source.

This change in fuel use is one reason ketogenic diets can lead to weight loss. However, here’s something important:

Eating more fat doesn’t automatically mean you’ll lose weight.

Fat contains approximately 9 calories per gram, compared with around 4 calories per gram for carbohydrate, and for protein. Portion sizes, and overall energy intake, and therefore still matter.

Research suggests that low-carbohydrate and ketogenic diets can produce weight loss and improvements in some metabolic markers.

What Kind of Fat?

This is where I think the phrase ‘healthy high-fat diet’ becomes important, because not all fats are equal.

A diet containing foods such as:

• Oily fish
• Nuts and seeds
• Avocados
• Extra-virgin olive oil
• Eggs
• Vegetables
• Lean or minimally processed meats

is very different from one that simply adds large quantities of butter, processed meats, fried foods, and highly processed, products.

Research also suggests that ketogenic diets can improve triglycerides and HDL cholesterol in some people, but may increase LDL and total cholesterol. The long-term effects on cardiovascular outcomes remain uncertain.

So, ‘high fat’ doesn’t automatically mean ‘healthy fat.’

The quality of the food still matters.

What Is Ketosis?

Ketosis is a metabolic state in which the body produces ketones from fat, which can then be used as an energy source.  Nutritional ketosis is usually achieved by substantially restricting carbohydrate intake.

It’s important, however, not to confuse nutritional ketosis with diabetic ketoacidosis, which is a potentially dangerous medical condition.

Being in ketosis doesn’t automatically mean that a ketogenic diet is healthier than every other way of eating.  Different approaches work for different people.

What About Autophagy?

You may have heard that ketogenic diets and fasting ‘switch on’ Autophagy, sometimes described as the body’s cellular recycling system. It’s an interesting area of research, and one where there is still much to learn.

Could a High-Fat, Low-Carb Diet Work for You?

It might.

Research suggests that low-carbohydrate and ketogenic diets can be effective for weight loss,  and that they can improve some metabolic markers, particularly in the short term; but there is no single diet that works perfectly for everyone.

If you’re considering reducing carbohydrates, you don’t necessarily have to change everything overnight.

You could start by:

• Reducing highly processed carbohydrate-rich foods
• Eating more vegetables
• Including a good source of protein with meals
• Choosing healthier sources of fat
• Reducing sugary foods and drinks
• Drinking enough water
• Paying attention to portion sizes
• Continuing to exercise

Give yourself time.  Some people thrive on a lower-carbohydrate approach. Others don’t. Some people enjoy fasting, while others simply feel miserable doing it. We’re all different.

The most effective way of eating is often the one that provides nutritious food, supports your goals, and perhaps most importantly, is something that you can actually maintain.

Healthy eating isn’t about finding the most ‘restrictive diet;’ it’s about finding an approach that is healthy for you, and which, can become a lifestyle, rather than a short-term restrictive eating plan. As always, consult an appropriate healthcare professional before trying to follow a low carb high fat diet.

Disclaimer

The information provided in this article, and on this website, is for general educational and informational purposes only. It is not intended to replace medical advice, diagnosis or treatment from a qualified healthcare professional.

If you experience rapid or unexplained weight loss or weight gain, persistent abdominal swelling or bloating, significant changes in your bowel habits, abdominal pain, or any other symptoms that concern you, please speak to your doctor.

If you are new to exercise, have an existing medical condition, are taking medication, or are unsure whether a particular exercise, diet or weight-loss approach, is suitable for you, speak to your doctor or another appropriately qualified healthcare professional, before starting or changing, your exercise programme.

Research is continually evolving, and individual responses to diet, exercise, sleep and weight loss, can vary considerably.

 

 

Research & Further Reading

Zhao et al. (2026) — Ketogenic diet-induced changes in adult lipid metabolism: A comprehensive systematic review and meta-regression of randomized controlled trials
A systematic review and meta-regression of 53 randomised controlled trials. The review found reductions in triglycerides and increases in HDL cholesterol, but also increases in LDL and total cholesterol. Long-term cardiovascular effects remain uncertain.

Amini et al. (2024) — Effect of ketogenic diet on blood pressure: A GRADE-Assessed systematic review and meta-analysis of randomized controlled trials
A systematic review and meta-analysis of randomised controlled trials examining the effects of ketogenic diets on blood pressure.

Cheng et al. (2024) — Impact of a ketogenic diet as a dietary approach on cardiovascular disease risk factors: A meta-analysis of randomized clinical trials
A meta-analysis of 27 randomised trials examining weight, triglycerides, blood glucose, insulin and cholesterol.

Patikorn et al. (2023) — Effects of ketogenic diet on health outcomes: An umbrella review of meta-analyses of randomized clinical trials
An umbrella review covering 17 meta-analyses and 68 randomised controlled trials, examining outcomes including body weight and triglycerides while highlighting increases in LDL cholesterol and limited long-term outcome data.

Amiri et al. (2024) — Impact of very low carbohydrate ketogenic diets on cardiovascular risk factors among patients with type 2 diabetes: GRADE-assessed systematic review and meta-analysis of clinical trials
A systematic review and meta-analysis of 29 trials examining outcomes including glucose, HbA1c, insulin resistance, triglycerides and blood pressure.

Choy & Louie (2023) — The effects of the ketogenic diet for the management of type 2 diabetes mellitus: A systematic review and meta-analysis of recent studies
A systematic review and meta-analysis examining ketogenic diets, weight, glycaemic control and cardiovascular risk factors in adults with type 2 diabetes.