Dietary Fat

Dietary fat is a source of energy and has several important roles in the body. It supplies essential fatty acids, helps the body absorb vitamins A, D, E and K, and forms part of the membranes surrounding our cells. The amount of fat we eat also affects how much energy we obtain from food and how our bodies use different fuels.

Different foods contain different types of fat in different proportions. It is therefore important to distinguish between the effects of an individual nutrient, the effects of a whole food and the effects of an overall diet.

At Healing by Nutrition, we are interested in how dietary fat fits into everyday meals, low-carbohydrate eating and strength training. This page explains the main considerations in practical terms, while distinguishing established facts from areas where the evidence remains limited.

1. Should We Eat the Fat on Meat?

Fat is a natural part of meat. Depending on the cut, it may be found around the outside, between the muscles or within the meat itself. It contributes to flavour, texture and energy.

When we eat meat with its fat, we obtain both protein and fat from the same food. Protein supplies amino acids needed to maintain and repair tissues, including muscle. Fat provides energy and essential fatty acids.

For people following a low-carbohydrate diet, fat can provide a substantial share of their daily energy because they eat fewer carbohydrates. People following a carnivore diet may also rely heavily on fat from meat and other animal foods.

There is no general requirement to remove all visible fat from meat. Whether someone prefers leaner or fattier cuts depends on their appetite, energy needs, food preferences and overall diet.

It is equally important not to assume that everyone needs the same amount of fat. Someone eating more carbohydrates may obtain more energy from them, while someone eating very few carbohydrates may obtain more energy from fat.

The practical point: Fat on meat is food, not something that automatically needs to be cut away. The amount that suits a person depends on the rest of their diet and their individual needs.

2. Eating Fat Versus Burning Body Fat

Dietary fat and body fat are related, but they are not the same thing.

Dietary fat is the fat we eat. It supplies energy and other materials the body needs.

Body fat is energy stored in the body. The body can draw on these stores when it needs more energy than it is receiving from food.

Fat provides approximately 9 calories per gram. Protein and carbohydrate each provide approximately 4 calories per gram. This means that a meal containing a lot of fat can supply considerable energy, even if the portion does not look particularly large.

When carbohydrate intake is very low, the body generally relies more heavily on fat for fuel. The liver can also produce ketones from fat, which the body can use as an energy source. This state is called nutritional ketosis.

However, being in ketosis does not automatically mean that someone is losing body fat. The body can use fat from food as well as fat stored in the body. If the energy supplied by food consistently exceeds the body's needs, body-fat loss may not occur even when carbohydrate intake is very low.

Conversely, a person can lose body fat without following a ketogenic diet. The type of diet affects how the body obtains fuel, but it does not remove the basic relationship between energy intake, energy use and changes in body stores.

The practical point: Eating more fat changes the amount of energy supplied by food. It does not, by itself, guarantee either weight loss or weight gain.

3. Lean Meat, Fatty Meat and Protein

Lean meat and fatty meat can both supply substantial amounts of protein. Their main difference is the amount of fat and therefore the amount of energy they provide.

A very lean cut may provide plenty of protein but relatively little energy from fat. A fattier cut provides protein alongside more energy from fat.

This distinction can matter when someone eats a diet based largely on meat. If the meat is consistently very lean and few other energy sources are included, total energy intake may be lower than intended. Some people may find it difficult to eat enough food to meet their energy needs when their meals are very lean.

That does not mean lean meat is inherently bad, or that everyone must add large amounts of fat. It means that protein intake and energy intake are two different considerations.

What about fat-to-protein ratios?

People following low-carbohydrate or carnivore diets sometimes use a fat-to-protein ratio to describe their food intake. The ratio may be expressed by weight or by calories, and those are not the same calculation.

For example, 100 grams of pure fat provides about 900 calories, while 100 grams of protein provides about 400 calories. A one-to-one ratio by weight therefore supplies considerably more energy from fat than from protein.

The ratio in a piece of meat is not necessarily the same as the ratio in a whole meal or across an entire day. Meat cuts differ, and people may also eat eggs, dairy products or other foods, depending on their chosen diet.

There is no single fat-to-protein ratio that everyone must follow. Appetite, activity, body size, food choices and personal goals all affect what works in practice.

The practical point: Consider both protein and total energy. A diet can provide plenty of protein while still supplying too little or too much overall energy for a person's needs.

4. Fat, the Brain and Hormones

Fat has several roles in the body beyond supplying energy.

The membranes surrounding our cells contain fats. Certain fatty acids are essential, meaning the body cannot make enough of them and must obtain them through food. Some long-chain fatty acids, including DHA, are important components of the brain and nervous system.

Dietary fat also helps the body absorb vitamins A, D, E and K. These vitamins have different roles, including supporting vision, bone health, normal blood clotting and the protection of cells. The amount and availability of these vitamins depend on more than fat intake alone, but a diet that contains virtually no fat can make their absorption more difficult.

Cholesterol is also used to make steroid hormones, including testosterone, oestrogen and cortisol. However, the fact that fat and cholesterol are involved in hormone production does not mean that eating more fat will necessarily increase hormone levels.

Research on dietary fat and sex hormones has produced mixed findings. A 2025 systematic review and meta-analysis of 11 trials involving 888 participants found no significant overall differences in the measured sex hormones between low-fat and high-fat diets. The authors noted that the evidence was of low certainty and that the number and quality of studies limited the conclusions that could be drawn. [1]

This means we should not assume either that a low-fat diet inevitably disrupts hormones or that a high-fat diet automatically improves them.

The practical point: Fat is needed for several normal body functions, but more dietary fat does not automatically mean better hormone levels or better health.

5. Cholesterol: What the Body Needs and What Blood Tests Measure

Cholesterol is a waxy substance that the body uses to build cell membranes and make certain hormones, vitamin D and bile acids. The body produces cholesterol itself, and it also absorbs some from food.

Cholesterol in food and cholesterol measured in the blood are related, but they are not interchangeable. The effect of dietary cholesterol on blood cholesterol varies between people and depends on the overall diet and individual biology.

Blood tests often report total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides. These measurements provide different information.

LDL particles carry cholesterol through the bloodstream. Higher levels of LDL cholesterol are associated with increased cardiovascular risk. HDL cholesterol is involved in transporting cholesterol back towards the liver, while triglycerides are another type of fat carried in the blood.

A change in one measurement should be interpreted in context rather than used as the only measure of a person's health. At the same time, a substantial rise in LDL cholesterol should not simply be dismissed because someone feels well or has lost weight.

A small randomised feeding trial in healthy, young, normal-weight women found that a ketogenic low-carbohydrate, high-fat diet increased LDL cholesterol over four weeks. The study was small, so its findings cannot predict the response of every person or establish the long-term effects of every ketogenic diet. It does, however, show that LDL cholesterol can rise in some people eating a high-fat, low-carbohydrate diet. [2]

The practical point: Dietary fat can affect blood lipid measurements, but responses vary. Blood results can provide useful information that cannot be determined from appearance, appetite or how someone feels alone.

6. Fat, Energy and Physical Performance

The body can use fat and carbohydrate to provide energy for physical activity. The balance between these fuels depends on factors such as exercise intensity, duration, training status and diet.

Fat is an important energy source during rest and lower-intensity activity. During harder efforts, the body generally relies more heavily on carbohydrate because it can supply energy quickly. This does not mean that a person must eat a high-carbohydrate diet to exercise, but it helps explain why different eating patterns may affect different types of activity in different ways.

People who eat very few carbohydrates may adapt to using fat and ketones more readily. However, becoming more accustomed to using fat does not guarantee improved performance in every type of exercise.

A systematic review and meta-analysis of 18 studies in athletes and trained adults found that ketogenic diets were not suitable for improving one-repetition maximum strength or high-intensity cyclic performance. Results varied with the type of exercise and the characteristics of the participants. [3] This research examined whole dietary patterns, not dietary fat in isolation.

Strength training also requires adequate total energy, sufficient protein, recovery and progressive training. Adding more fat to a diet cannot replace these requirements.

The practical point: Fat can contribute substantially to energy needs, especially during lower-intensity activity and low-carbohydrate eating. The effect of a particular diet on performance depends on the person and the type of exercise.

7. Does Fat Help Us Feel Full?

Fat contributes to the taste, texture and energy content of food. Many people find meals containing meat and its natural fat satisfying, and a satisfying meal may help them go longer before wanting to eat again.

However, fullness is influenced by several things, including the amount of food eaten, protein content, food texture, eating speed, individual appetite and the composition of the whole meal.

Fat is energy-dense, so a small quantity can add a substantial amount of energy to a meal. Adding more fat does not guarantee a proportionate increase in fullness. Some people feel satisfied by fattier meals, while others prefer leaner food or find very fatty meals uncomfortable.

A systematic review of short-term studies found that the effects of dietary fat on fullness were variable; fat does not invariably produce a stronger feeling of fullness for each calorie consumed. [4] These findings do not mean that fatty meals cannot be satisfying. They mean that the response is not the same for everyone.

Appetite can also change as someone changes their eating pattern. A person's experience during the first days or weeks of a diet may differ from how they feel after adapting to it.

The practical point: Use appetite and personal experience as useful information, but do not assume that more fat will always make a meal more satisfying or that everyone needs the same amount.

8. Fat Digestion, Bowel Movements and Gallstones

Dietary fat is digested with the help of bile, a fluid made by the liver and stored in the gallbladder. When fat enters the small intestine, bile helps break it into small droplets so digestive enzymes can act on it. The resulting fatty acids and other products can then be absorbed.

Most dietary fat is absorbed in the small intestine. When digestion or absorption is disrupted, symptoms can occur. These may include loose stools, diarrhoea, greasy or difficult-to-flush stools, bloating or abdominal discomfort. Such symptoms can have several causes and should not automatically be blamed on the amount of fat someone eats.

Can eating more fat cause diarrhoea?

Some people experience loose stools or urgency after particularly fatty meals. In other cases, diarrhoea may be related to a digestive condition, medication, infection or a problem with bile acid handling.

Bile acid diarrhoea occurs when bile acids reach the large intestine in excessive amounts and cause watery stools. It is a specific condition, not a general response that everyone should expect from eating fat.

Persistent diarrhoea, greasy stools or unexplained digestive symptoms warrant appropriate medical assessment rather than simply cutting out fat or continuing to increase it.

Can eating more fat help constipation?

Constipation can involve infrequent bowel movements, hard stools, straining or a feeling that the bowel has not emptied completely. Its causes vary and can include changes in food intake, fluid intake, activity, medication and underlying health conditions.

A change in dietary fat may affect bowel habits for some people, but fat is not a universal treatment for constipation. Nor does eating a low-carbohydrate diet automatically mean someone will become constipated. The overall diet and the individual's response matter.

Dietary Fat and Gallstones

The gallbladder stores bile, a fluid produced by the liver that helps the body digest and absorb fat. When we eat a meal containing fat, the gallbladder contracts and releases bile into the small intestine.

Gallstones are solid deposits that form in the gallbladder. They can remain unnoticed, but some cause pain or other complications. Risk factors include factors that affect the composition of bile and how the gallbladder empties. Rapid weight loss and prolonged periods of very low food intake can also increase the risk of developing gallstones.

Eating fat is not, by itself, a simple explanation for why gallstones develop. Although fat stimulates the gallbladder to empty, research has not established that a high-fat diet universally prevents gallstones or that dietary fat alone causes them.

Some people who already have gallstones experience pain after eating, sometimes following a fatty meal. Anyone experiencing repeated abdominal pain or suspected gallbladder symptoms should seek medical assessment rather than attempting to treat the problem by changing fat intake alone.

A Cochrane review found that there was not enough reliable clinical evidence to determine whether changing dietary fat improves gallstone disease. [5]

The practical point: Fat has a normal role in gallbladder function, but gallstones have several contributing factors. Neither increasing fat nor eliminating it should be presented as a proven general treatment for gallstones.

9. Cooking Fats: Is Beef Tallow a Good Choice?

Beef tallow is rendered beef fat. It has been used in cooking for generations and can be used for frying, roasting and other cooking methods.

Tallow contains a mixture of saturated, monounsaturated and polyunsaturated fatty acids. Its precise composition varies with factors such as the animal and the fat used to make it. It is therefore inaccurate to describe tallow as consisting entirely of saturated fat.

As with other cooking fats, how tallow is used matters. Fat can deteriorate when exposed to excessive heat for too long, particularly when it is repeatedly heated and reused. Avoiding prolonged overheating and discarding fat that has deteriorated are sensible cooking practices.

Different fats also behave differently during cooking. Their composition, flavour and suitability depend on the food and cooking method. There is no need to assume that one cooking fat is the only acceptable choice for every person or every recipe.

This page does not repeat the separate discussion of seed oils. The important point here is that beef tallow is a traditional cooking fat that can be used in ordinary cooking. Its presence of saturated fatty acids is not, by itself, a reason to label it unsuitable for cooking.

The practical point: Beef tallow is a legitimate cooking fat. Use it in a way that suits the food and cooking method, and avoid repeatedly overheating it.

10. Saturated Fat: What Can We Conclude?

Saturated fat is found in a range of foods, including beef, lamb, butter, cheese and beef tallow. It is one type of fatty acid, and a food's saturated-fat content is only one part of its composition.

Research has examined what happens when people reduce their saturated-fat intake over time. A Cochrane review of long-term trials found that reducing saturated fat was associated with fewer combined cardiovascular events. The results did not establish that every food containing saturated fat has the same effect, nor did they test beef tallow as a single food in isolation. The review was funded by the World Health Organization, rather than by a food-industry sponsor. [6]

This distinction matters. Evidence about changing the overall amount of saturated fat in a diet cannot automatically be translated into a verdict on one particular food. Beef tallow contains a mixture of fatty acids, and people use it in different quantities and within different dietary patterns.

Blood cholesterol is also relevant. Saturated fat can raise LDL cholesterol in some people, although the size of the response varies. A meaningful change in blood lipids should be considered alongside the person's overall circumstances rather than ignored or treated as the sole measure of health.

There is not enough direct clinical evidence to conclude that beef tallow itself causes cardiovascular disease in every dietary context. Equally, the absence of direct trials on tallow does not establish that consuming unlimited amounts is risk-free.

The practical point: Saturated-fat content alone does not tell the whole story about a food. Beef tallow can be used as a cooking fat, while questions about overall dietary patterns and individual blood results should be considered separately.

11. How Much Fat Should We Eat?

There is no single amount of dietary fat that suits everyone. Needs and preferences vary with body size, activity, appetite, food choices and the overall pattern of eating.

Someone eating a low-carbohydrate or ketogenic diet will generally obtain a larger share of their energy from fat than someone eating a diet with more carbohydrates. Someone following a carnivore diet may obtain much of their energy from the fat naturally present in meat and other animal foods.

The amount of fat eaten also affects total energy intake. Because fat provides about 9 calories per gram, adding substantial amounts of it to meals can increase energy intake considerably. For someone trying to gain weight or meet high energy needs, this may be useful. For someone trying to reduce body fat, it is worth remembering that dietary fat is still a source of energy, even when carbohydrate intake is very low.

There is no universal fat-to-protein ratio that everyone must follow. Ratios used by people following particular diets are approaches to organising food intake, not requirements that apply to every person.

A practical starting point is to consider whether meals provide enough protein and energy, whether the diet is sustainable, how appetite and digestion respond, and whether the person's goals are being met. People with medical conditions or a history of digestive problems may need individual advice.

The practical point: The appropriate amount of fat depends on the whole diet and the individual. A fixed number or ratio should not be treated as a rule for everyone.

12. Paleo, Keto, Ketovore and Carnivore: Where Does Fat Fit In?

Different dietary patterns include different amounts of fat and carbohydrate. The names describe broad approaches rather than a single fixed menu.

• Paleo: Usually focuses on foods such as meat, fish, eggs, vegetables, fruit, nuts and seeds, while excluding or limiting foods such as grains and many highly processed products. Fat intake varies depending on food choices.

• Ketogenic (keto): Restricts carbohydrate sufficiently to encourage the body to produce ketones. Fat commonly supplies a substantial share of energy, but the exact amount varies.

• Ketovore: A term used for an approach that combines ketogenic eating with a stronger emphasis on animal foods. There is no single standard definition.

• Carnivore: Focuses on animal foods, commonly meat, fish, eggs and sometimes dairy. Depending on the foods selected, fat may provide a large share of total energy.

These diets are not interchangeable. A ketogenic diet can include plant foods, while a carnivore diet excludes them or limits them to virtually none. Even within the same named diet, people may eat very different amounts of fat and protein.

Research on carnivore diets remains limited. A 2026 scoping review identified only nine human studies and concluded that the evidence was very limited because studies tended to be small, short and without control groups. The review's authors declared no conflicts of interest, but its findings cannot establish the long-term effects of the diet with confidence. [7]

The practical point: The amount and source of dietary fat depend on the dietary pattern. The label alone does not tell us exactly what someone eats, how much energy they consume or how they respond.

Our Perspective at Healing by Nutrition

At Healing by Nutrition, we are interested in real food, practical cooking and the way different eating patterns fit into everyday life. Our own experiences influence the questions we ask, but personal experience is not the same as proof that a particular diet will produce the same result for everyone.

Dietary fat has several important functions. It can supply energy, contribute to satisfying meals and form part of a low-carbohydrate or animal-based way of eating. At the same time, no single number, food or dietary pattern provides a complete answer for every person.

The useful question is how the food choices, total diet and individual response fit together.

Scientific References

[1] Soltani S, Hejazi M, Meshkini F, et al. The Effect of Low-Fat Diets Versus High-Fat Diet on Sex Hormones: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Journal of Food Science. 2025;90(5).

[2] Burén J, Ericsson M, Damasceno NRT, Sjödin A. A Ketogenic Low-Carbohydrate High-Fat Diet Increases LDL Cholesterol in Healthy, Young, Normal-Weight Women: A Randomized Controlled Feeding Trial. Nutrients. 2021;13(3):814.

[3] Koerich ACC, Borszcz FK, Mello AT, de Lucas RD, Hansen F. Effects of the ketogenic diet on performance and body composition in athletes and trained adults: A systematic review and Bayesian multivariate multilevel meta-analysis and meta-regression. Critical Reviews in Food Science and Nutrition. 2023;63(32):11399–11424.

[4] Warrilow A, Mellor D, McKune A, Pumpa K. Dietary fat, fibre, satiation, and satiety—a systematic review of acute studies. European Journal of Clinical Nutrition. 2019;73:333–344.

[5] Madden AM, Smeeton NC, Culkin A, Trivedi D. Modified dietary fat intake for treatment of gallstone disease in people of any age. Cochrane Database of Systematic Reviews. 2024;(2).

[6] Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews. 2020;(8).

[7] Lietz A, Dapprich J, Fischer T. Carnivore Diet: A Scoping Review of the Current Evidence, Potential Benefits and Risks. Nutrients. 2026;18(2):348.