Journal Club 1

Question 1

What was the study that was looked at?

Answer 1

Looking at ultra-processed diets and their effect on calorie intake and weight gain

Hall et al, 2019

Question 2

INTRO - why was the work done?

Answer 2

The increased availability and consumption of ultra-processed food have been associated with rising obesity prevalence

• but scientists have not yet demonstrated the causal link between the two
• this is exactly what this study showed

Question 3

What were the aims of the study?

Answer 3

Aim - whether ultra-processed foods affect ad libitum (diet available at all times) energy intake + cause body weight change

Question 4

What was the study setting like?

Answer 4

Participants were required to stay in a hospital facility 24/7 for 28 days straight

i.e a very controlled randomised study (artificial)

Question 5

What was the eligibility criteria?

Age, BMI + any exclusion criteria

Answer 5

Age - 18-50 yrs
BMI - greater than 18.5 kg.m2
Weight stable - less than +/-5% over last 6 months

Exclusion…
1. Medical conditions - cancer, anaemia, diabetes, psychiatric conditions etc
2. Dietary restrictions - food allergies, adherence to some foods

Question 6

What style of study was it - include primary + secondary outcomes

Answer 6

A randomised controlled trial - cross over trial comparing ultra-processed diet and unprocessed diets

1. Primary outcome = energy intake measured as ad libitum energy intake
2. Secondary outcomes = appetite + sensory assessment, body weight + composition, blood biomarkers

Question 7

What were the participants like?

Answer 7

20 participants (10 male + 10 female)

• average age of 31.2 yrs old + all obese (BMI 27 avg)

Question 8

Describe the 2 interventions

Answer 8

Intervention - exposed to ultra-processed or unprocessed diets for 14 days

Meal structure - 3 meals a day + unlimited access to snacks

Instructions - consume as much or as little food as desired by them

• blinded to their body weight during study

Question 9

Were the diets adequately matched for nutrient intake?

Answer 9

Meals / diets were designed to be matched for presented calories, energy density, macronutrients, sugar, sodium + fibre

Question 10

What were the key results regarding food / energy intake?

Answer 10

Metabolised energy was greater during ultra-processed diet - independent of diet assessment, sex + BMI

• due to consuming more carbs + fat but not protein

UP diet increased energy intake at breakfast + lunch but not at dinner (+500kcal per day)

Question 11

Why did the UP diet group consume more carbs + fat but not protein, what’s the reason for this?

Answer 11

Protein leverage could explain roughly 50% of observed energy differences

• its a dietary regulation mechanism = humans have an ‘inherent’ need to maintain their protein intake + protein is prioritised in our diets
• therefore protein intake was matched across the 2 diets

Question 12

What did the results show on appetite?

Answer 12

No significant difference in pleasantness or familiarity of meals between ultra-processed + unprocessed diets

• PYY (appetite suppressing hormone) increased during unprocessed diet vs baseline + UP diet
• Ghrelin (hunger hormone) decreased during unprocessed diet vs baseline

Question 13

What did the results show on meal eating rate?

Answer 13

UP diet consumed meals sig. faster than unprocessed

• could be due to foods being softer

Question 14

What did the results show on body weight?

Answer 14

1. UP diet gained body mass (+0.4kg)
2. Unprocessed diet lost body mass (-0.3kg)

• both were significant differences from baseline

Question 15

Therefore, what can be concluded from the results?

Answer 15

Eliminating UPF from diet decreased energy intake + resulted in weight loss whereas consuming more UPF increases energy intake + causes weight gain

• therefore limiting UPF can be effective for obesity prevention + treatment

Question 16

What were some key strengths of the study?

Answer 16

1. In-patient experimental approach - controlled conditions and close monitoring
2. Cross-over study design - reduces variability by having participants serve as their own controls
3. Depth, detail and rigour of analyses - ensures comprehensive and thorough evaluation of findings

Question 17

What were the key weaknesses of the study?

Answer 17

1. No washout periods between diets - this could lead to carryover effects
2. Relatively short-term study - limits the ability to assess long-term effects
3. Inpatient setting - results may not be generalisable as conditions do not reflect typical real-world settings