- Title
- Role of long chain omega-3 polyunsaturated fatty acids on weight management
- Creator
- Munro, Irene A.
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2013
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Despite an ever-growing body of research on obesity, investigating causes and possible solutions to address the problem, the prevalence of obesity continues to escalate. A major cause of obesity is attributed to poor eating behaviours driven by food advertising, lack of nutrition knowledge, lack of physical activity, lack of time and lack of will power to control food intake, and there is a plethora of research with a focus on changing dietary behaviour for weight management. In part, this research also addressed dietary change, employing a reduced energy intake for weight loss supported with nutrition education and counselling to enable maintenance of the weight lost. However, consideration was also given to the internal interactions and changes that occur in the body when energy intake exceeds energy output resulting in weight gain and obesity, and whether these mechanisms could be manipulated to reduce weight gain through the inclusion of long chain omega-3 polyunsaturated fatty acids (LCω-3PUFA) in the diet. Prospective studies in humans have reported that high levels of LCω-3PUFA were associated with low levels of obesity in males while higher intakes of LCω-3PUFA were associated with higher rates of obesity in females. The data on LCω-3PUFA concentrations in males and females had been sourced from dietary records with questionable reliability. Thus the first aim of this research was to investigate whether there was a relationship between plasma LCω-3PUFA and weight status in humans. The first research chapter (Chapter 3) reports on the relationship observed between plasma LCω-3PUFA composition and weight status in free living adults. Obese individuals, both males and females, had significantly lower levels of LCω-3PUFA compared to healthy-weight individuals. Thus the aim of the first clinical trial (Chapter 4) was to investigate whether LCω-3PUFA supplementation, combined with a healthful diet with portion control and energy restriction would facilitate weight loss, improve blood lipids and inflammatory mediators. This was a double-blinded randomised controlled trial with two parallel groups. Both groups were instructed to follow the same diet for 12 weeks, one group consumed fish oil capsules and the other group consumed placebo capsules (monounsaturated oil). Despite a two-fold increase of EPA and DHA in the treatment group, there were no significant differences in outcome measures between the two groups. Both the placebo and the fish oil supplemented groups lost similar amounts of weight, fat mass and fat free mass. Overall dietary compliance was poor representing a possible confounding factor on the outcomes. The aim of the next clinical trial (Chapter 5) was to investigate whether LCω-3PUFA supplementation would facilitate weight loss, but this time in combination with a very-low-energy-diet (VLED), using meal replacements (MRs), to improve dietary compliance. The protocol for this trial was the same as the previous one apart from the change to the diet and with a shortened intervention of 4 weeks. Also, because of the anticipated rapid weight loss, a 10 week weight maintenance phase with continued supplementation was included. Although there was a greater than two-fold increase of EPA and DHA in the treatment group, there were no significant differences in outcome measures between the two groups after 4 weeks of weight loss. However, after a further 10 weeks of supplementation during weight maintenance, there was a significant reduction in anthropometric measurements, apart from fat free mass, in the treatment group but not the placebo group. The differences between the two groups were not significant. The final clinical trial (Chapter 6) investigated potential benefits of loading the body cells/membranes with LCω-3PUFA prior to following a weight loss program. The protocol for the trial was similar to the previous two, but commenced with 4 weeks of prior-supplementation with fish oil or placebo in the treatment and placebo groups, respectively, while consuming their usual diet. This was followed by 4 weeks of dietary intervention where both groups again consumed a VLED with MRs plus continued supplementation. The same measurements were taken as for the previous trials. After 4 weeks of prior-supplementation there were no significant differences in outcome measures for either group. However, at 8 weeks a significant 3-way interaction between time, group and gender was observed for percentage reduction in weight and BMI, suggesting a significant effect of LCω- 3PUFA for the fish oil group. There was also a significant reduction in percentage weight loss for females in the fish oil group. These results suggest that priorsupplementation with LCω-3PUFA, followed by supplementation with LCω-3PUFA and a VLED regimen may assist weight loss.
- Subject
- weight management; obesity; dietary behaviour; polyunsaturated fatty acids; nutrition; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/937489
- Identifier
- uon:12572
- Rights
- Copyright 2013 Irene A. Munro
- Language
- eng
- Full Text
- Hits: 2396
- Visitors: 2517
- Downloads: 371
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Abstract | 432 KB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Thesis | 3 MB | Adobe Acrobat PDF | View Details Download |