necessary calories. In this case, the use of calorically dense foods such as mayonnaise and
vegetable oils can be used to increase caloric intake. If appetite is not suppressed on a ketogenic
diet, less calorically dense foods can be consumed.
Cholesterol levels
The relatively high fat intake of the ketogenic diet immediately raises concerns regarding
the effects on blood lipids and the potential for increases in the risk for heart disease, stroke, etc.
Several key players in relative risk for these diseases are low density lipoproteins (LDL, or ‘bad
cholesterol’), high density lipoproteins (HDL, or ‘good cholesterol’) and blood triglyceride levels
(TG). High levels of total cholesterol, and high levels of LDL correlate with increased disease risk.
High levels of HDL are thought to exert a protective effect against cholesterol-related disease.
The overall effects of implementing a ketogenic diet on blood cholesterol levels are far from
established. Early short-term studies showed a large increase in blood lipid levels (16,17).
However, later studies have shown either no change or a decrease in cholesterol levels (18-20).
One problem is that few long term studies are available on the ketogenic diet, except in
epileptic children. In this population, who are kept in deep ketosis for periods up to three years,
blood lipid levels do increase (21,22). However, the ketogenic diet is not thought to be atherogenic
due to the fact that any negative effects induced by three years in ketosis will be corrected when
the diet is ended (22).
It has been shown that Inuits, who maintain a ketogenic diet for long periods of time every
year, do not develop heart disease as quickly as other Americans (23), suggesting that there are
no long term effects. However, this may be related to the fact that a ketogenic diet is not
continued indefinitely. There may be a slow removal of cholesterol from the arteries during time
periods when a more balanced diet is being followed (23).
Most of the degenerative diseases thought to be linked to high blood lipid levels take years
(or decades) to develop. Unless an individual is going to stay on a ketogenic diet for extremely long
periods of time, it is not thought that there will be appreciable problems with cholesterol buildup.
From a purely anecdotal standpoint, some individuals who have undergone testing show a
complete lack of cholesterol buildup in their arteries.
Another problem is that weight/fat loss per se is known to decrease cholesterol levels and it
is difficult to distinguish the effects of the ketogenic diet from the effects of the weight/fat loss
which occurs. A few well designed studies allow us to make the following rough generalizations:
- If an individual loses weight/fat on a ketogenic diet, their cholesterol levels will go down
(18,24,25) ; - If an individual does not lose weight/fat on a ketogenic diet, their cholesterol levels will go up
(24,26).
As well, there can be a decrease followed by increase in blood lipid levels (27). This is
thought to represent the fact that body fat is a storehouse for cholesterol and the breakdown of
bodyfat during weight loss causes a release of cholesterol into the bloodstream (27). Additionally,
women may see a greater increase in cholesterol than men while on the ketogenic diet although
the reason for this gender difference in unknown (28). In practical experience however, there is a