Differential Metabolism of Dietary Fatty Acids
Condition: Obesity; Diabetes; Hyperlipidemia
MeSH terms: Hyperlipidemias
Study type: Interventional

Summary: 
      Differences in how diet fats are converted to energy could explain some of the reported
      differences in health effects among different classes of dietary fat (e.g. monounsaturated
      vs. saturated). Recently, this laboratory showed that monounsaturated fats are turned into
      energy more readily than saturated fats. These results may mean that if one feeds more
      monounsaturated fatty acids (MUFA) and less saturated fatty acids (SFA) in the diet, body fat
      might accumulate at a lower rate. This could affect the risk of obesity and Type 2 Diabetes.
      This project has two principal Specific Aims which will be assessed in healthy young adults
      who are fed liquid formulas containing either an approximately equal amount of MUFA and SFA
      (controls) or a much greater amount of MUFA and much less SFA:

        1. To determine if a higher intake of MUFA and a reciprocally lower intake of SFA is
           associated with a higher rate of fat oxidation. We hypothesize that the rate of fat
           oxidation after eating will be higher in those subjects randomized to the MUFA-enriched
           diet compared to controls.

        2. To measure energy intake required to maintain constant body weight during each diet and
           to measure fat-free mass and fat mass, before and after each dietary change. We
           hypothesize that those on the high MUFA diet will need a higher energy intake required
           to maintain constant body weight.
    

Detailed description: 
      Our Preliminary Data indicate that the rate of oleic acid (OA) oxidation (amount/unit time)
      is 21% increased compared to palmitic acid (PA) when both fatty acids are fed to the same
      person at the same intake. We hypothesize that if the ratio of OA to PA in the diet were to
      increase, the rate of total fatty acid oxidation in the fed state also would increase under
      the same metabolic conditions. If our principal hypothesis is correct, overall daily fat
      balance might be decreased in humans fed diets enriched in OA. This would have potential
      significance to the treatment and prevention of obesity.

      In order to address this hypothesis, we propose the following double-masked, randomized
      control trial. Indirect calorimetry will be performed in the fed and fasting state in young,
      healthy adults who will be studied under two conditions: after a 30-day, supervised, solid
      food diet and then again after a 30-day formula diet. The subjects will be randomized to
      receive either a Control Formula Diet of the same macronutrient and fatty acid composition as
      the solid food diet (OA=PA=16.4% total kcal) or a High Oleic Acid Formula Diet (OA=31.4%
      total kcal and PA=1.7% total kcal). The Control Diets (solid and liquid) provide amounts (per
      kcal) of total fat, saturated fat, and OA that are similar to the to the 50-75th percentile
      of intake of young adult Americans but above the intake of total fat and saturated fat that
      is recommended for optimal long-term health. The High OA Formula Diet is designed to simulate
      the fat source of the Mediterranean Diet. The High OA diet will result in a 167% increase in
      the intake/kcal of OA in the sn-1 and sn-3 positions of the dietary triacylglycerol. Using
      dual-energy x-ray absorptiometry (DEXA), we will monitor body composition before and after
      each diet, while adjusting energy intake to maintain constant body weight. The following
      Specific Aims will be addressed:

        1. To determine if a higher intake of oleic acid (and a reciprocally lower intake of
           palmitic acid) is associated with a higher rate of fat oxidation. We hypothesize that
           the rate of fat oxidation (g/hr) in the fed state, adjusted for the covariate effect of
           the rate of fat oxidation on the solid food diet, will be higher (>30%) in those
           subjects randomized to the OA-enriched diet compared to controls. Furthermore, we
           hypothesize that fat oxidation will not be higher when expressed as a proportion of
           energy expenditure in the OA-enriched formula group. That is, we expect energy
           expenditure in the fed state to be higher in those fed the OA-enriched diet.

        2. To measure energy intake required to maintain constant body weight during each diet and
           to measure fat-free mass and fat mass, before and after each dietary change. We
           hypothesize that a higher rate of fat oxidation on the high OA diet will be associated
           with a higher energy intake required to maintain constant body weight.

        3. To compare fat oxidation on the liquid formula diet with that observed on the solid food
           diet. We hypothesize that fat oxidation will increase in those fed the OA-enriched diet.

        4. To measure the thermic effect of feeding during both the solid food and formula diet
           periods. We hypothesize that the high OA feeding will be associated with a higher
           thermic effect of feeding.
    

Intervention name(s): Oleic acid (OA); Palmitic Acid (PA)
Intervention type(s): Dietary Supplement; Dietary Supplement
Intervention description(s): OA-enriched (HI OA; fat, 40%; PA, 1.7%; OA, 31.4%); PA-enriched (HI PA; fat, 40% of energy; PA, 16.8%; OA, 16.4%)
Intervention MeSH terms: Palmitic Acid
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: fatty acids; oleic acid; palmitic acid; fat oxidation; energy expenditure; body composition; monounsaturated fat; human