Fat, Carbs, Protein & Weight Loss
There are important differences in the
macronutrients' effect on energy balance and as a consequence diet composition
plays a role for weight loss and obesity.
Energy Balance in Fat, Carbs and Protein
The most important differences between macronutrients on energy balance
is exerted on appetite and energy intake: mechanistic and ad lib intervention
studies support that fat possesses a lower satiating power than carbohydrate
and protein, and a diet low in fat and high in carbohydrate and protein
therefore decreases energy intake. The differences between fats and carbohydrates
can partly be attributed to differences in energy density. The effect
of dietary fat on energy balance seems to be enhanced in susceptible subjects,
particularly sedentary individuals with a genetic predisposition to obesity.
There is some preliminary evidence to suggest that mono-unsaturated fat
is more fattening than poly-unsaturated fat, but randomised clinical trials
are lacking. A European multicenter trial CARMEN, which used the ad lib
intake design, could not find any difference between simple and complex
carbohydrates in their ability to produce weight loss in obese subjects.
Low Fat, High Protein Diets
Protein is more satiating than carbohydrate and intervention studies support
that low fat, high protein diets produce larger weight loss in obese subjects
than low fat, high carbohydrate diets. A protein rich diet also produces
a 2-4 percent larger increase in 24-h energy expenditure than a isoenergetic
carbohydrate rich diet, and the thermogenic effect of pork protein exceeds
that of soy protein by 2 percent.
During overfeeding the energetic efficacy
is lower on a low fat, high carbohydrate diet than on a high fat diet.
This is due to increased faecal energy loss, cost of de novo lipogenesis
and of increased thermogenesis most likely due to increased sympathetic
nervous system activity on the high carbohydrate diet.
Low Fat Diets & Body Weight
Clinically, low fat diets cause weight loss proportional to pre-treatment
body weight, and in a dose-dependent way, i.e. weight loss is positively
correlated to the reduction in dietary fat content. In a recent meta-analysis
we found that ad lib low fat intervention groups compared with ad lib
normal fat groups showed a greater weight loss and a greater reduction
in energy intake. A 10 kg higher pre-treatment mean body weight was associated
with a 2.6 kg greater difference in weight loss. After a major weight
loss an ad libitum low fat diet program is superior to calorie-counting
in maintaining the weight loss 2 years later.
In conclusion, calories from different
macronutrients are not equal in their effect on energy balance and propensity
to produce weight gain.
Source: Research Department of Human Nutrition,
RVA University, Rolighedsvej 30, 1958 Frederiksberg, Copenhagen, Denmark.
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