Popular weight loss diets – what does
the science say?
Popular Diets
• Higher protein diets
• Ketogeneic diet
• Intermittent fasting
• Mediterranean diet
• Paleolithic (Paleo) diet
• Commercial Programs - Weight Watchers
Higher Protein Diets
• What is this diet?
• Cutting carbohydrates and/or fats to reduce energy
• Maintaining protein intake ~ 1.2 – 1.6 g/kgBW/d
• Still within AMDR
• One of the most studied weight loss diets
• Many different forms (i.e. Zone vs. Atkins)
Higher Protein Energy Restriction Diet for a 65 kg,
somewhat active woman
Typical energy and
macronutrient intake
• Energy: 1997 kcal/d
• Carbohydrate: 250 g = 1000
kcal = 50% Ein
• Protein: 85 g (1.3 g/kgBW/d)
= 340 kcal = 17% Ein
• Fat: 73 g fat = 657 kcal = 33%
Ein
Energy restricted energy and
macronutrient intake
• Energy: 1498 kcal/d
• Carbohydrate: 177 g =708 kcal
= 47% Ein
• Protein: 85 g (1.3 g/kgBW/d) =
340 kcal = 23% Ein
• Fat: 50 g fat = 450 kcal = 30%
Ein
Protein and weight loss
Wycherly, Am J Clin Nutr, 2012
Protein and weight loss
Wycherly, Am J Clin Nutr, 2012
Protein and weight loss
Wycherly, Am J Clin Nutr, 2012
Why does it work better than other energy deficit diets?
Protein affects satiety
Weigle, Am J Clin Nutr, 82(1), 2005
Protein stimulates MPS
PROTEIN
Protein
Breakdown
Protein
Synthesis
AA
Hector, FASEB J, 2018; Stokes, Nutrients, 2018
Protein has a higher thermic effect of food
Morales, J Am Coll Nutr, 2017; Westerterp, Int J Obes Relat Metab Disord, 1999
Protein quality matters
3 oz serving
105 kcal
16 g protein
½ cup
110 kcal
7 g protein
1.25 cup skim
112 kcal
11 g protein
½ cup
111 kcal
4 g protein
So what do I do if I want to try this diet?
• Create a 500 – 1000 kcal/d energy deficit
• No more than a 40% decrease beyond energy needs
• Include whole grain carbohydrates and healthy fats
• Include protein foods ~1.2 – 1.6 g/kgBW/d
• 0.24-0.3 g/kgBW/meal (or 25-30g/meal)
• Eat the highest quality protein foods possible
• Eat foods, not supplements
Leidy, AJCN, 2015
Other benefits of higher protein diets
• Health benefits
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Lower waist circumference
Lower blood pressure
Higher HDL
Lower fasting insulin
Lower triglycerides
Maintenance of muscle mass
• No adverse effect on
• Bone
• Kidney function
Berryman, AJCN, 2016; Pasiakos, J Nutr, 2015; Santesso, Eur J Clin Nutr, 2012; Shams-White, AJCN, 2017; Devries, J Nutr, 2018
What is the Ketogenic Diet?
• A diet used to stimulate ketosis
• High fat, low CHO, usual protein
• < 50 g CHO/d
• ~15% Ein from protein
• Premise:
• Energy cost of producing ketone bodies
• Reduces insulin secretion
• Satiating effect of protein???
• Takes time to get into this state – have to be committed
Types of ‘Ketogenic’ Diets
Classical KD
Defined as <130 g carbohydrate per day or <26% of caloric intake by the
American Diabetes Association
Modified Atkins Diet
Very low-carbohydrate KD
65% caloric intake from fat, 30% protein, 6% carbohydrates
Carbohydrates < 30 g/day
Table 1. Standard composition of ketogenic diets in adults * (calculated for a 2000 kcal diet/day).
KD, Ketogenic Diet. * Adapted from Kossoff et al. [15], Feinman et al. [16], Accurso et al. [17].
¾ c = 17g
1 slice = 14g
1 medium = 25g
1 cup = 27g
Kosinski, Nutrients, 2017
A typical keto meal?
Keto diet in the media
Keto diet studied in research
The people who are for it say…
• Reduces:
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Body weight
Blood sugars
Blood pressure
Chronic pain
Inflammation
Medication use
• Improves:
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Lipid profile
Energy
Sleep
IBS symptoms
The people who are against it say…
• Increases risk of nutrient deficiency
• Induces liver problems
• Leads to constipation
• Leads to fuzzy thinking and mood swings
• Increases risk of NAFLD, CVD, T2D long-term
What does the science say?
Bueno, Br J Nutr, 2013
What about the effects on health?
Kosinski, Nutrients, 2017
What ‘ketogenic diet’ is being studied?
• Varies
• Benlloch, Nutrients, 2019 – 40% fat, 40% carbs, 20% protein
• Moreno, Endocrine, 2014
• Active: < 50g/d CHO, 25g/d fat, 0.8-1.2g/kgBW protein
• Wilson, J Str Cond Res, 2017 – 75% fat, 5% carbs, 20% protein
• Gomez-Arbelaez, Nutr Metab, 2018 – same as Moreno
• Not all diets being called ‘keto’ are truly ‘ketogenic diets’
• Need to make sure you are reviewing the correct literature when looking at
effectiveness and long-term health risks/benefits
What happens when you stop the ketogenic diet?
• Most regain the weight
• Have to be careful – come off of the diet slowly
So what do I do if I want to try this diet?
• Create a 500 – 1000 kcal/d energy deficit
• Include healthy fats and high quality proteins
• Get the biggest nutrient bang for your buck when eating your 50 g of
carbohydrates
• Different colour veggies
• Remember that it takes ~3 days to get into a ketogenic state and one
high carb meal will kick you out of ketosis
• Consider taking a multivitamin
Intermittent Fasting
• What is this diet?
• Use short-term fasting to reduce energy intake
• 3 main types
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Alternate
Ad libitum
day fasting
25% kcal
Ad libitum
25% kcal
Ad libitum
25% kcal
Ad libitum
Timerestricted
fasting
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
16-20 h
fast, 4-8 h
feeding
Whole-day Ad libitum
fasts
Ad libitum
Ad libitum
Ad libitum
or 24h fast
Ad libitum
Ad libitum
24 h fast
Tinsley, Nutr Rev, 2015
What does the science say?
• Alternate and whole-day fasting
• Reduced body weight, fat-mass
• Fat-free mass lost if true fasting day
• Improved health outcomes: cholesterol, TG, LDL
• Time-restricted
• Not well studied yet
• Compared with continuous energy restriction – similar results
• Potentially greater benefit in preventing weight regain
Seimon, Mol Cell Endocrinol, 2015; Tinsley, Nutr Rev, 2015; Zuo, Front Physiol, 2016
So what do I do if I want to try this diet?
• Choose which approach best suits your lifestyle
• Focus on eating whole-grains, healthy fats and high-quality proteins
• Keep track of what you are eating to ensure that over the course of
the week you are in a caloric deficit
Mediterranean Diet
• What is this diet?
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High in fat
Low in saturated fat
Very low in trans fat
Rich in monounsaturated fat
Rich in complex CHO and fibre
Rich in nutrients and phytochemicals
• Whole foods: bread, whole grains, pastas, veg & fruit, legumes,
yogurt, cheese, nuts, fish & poultry, eggs
• Well known for its health benefits – particularly reduced CVD
The Mediterranean Diet
Is it better for weight loss than other diets?
• Systematic review
• Compared to low-fat or low-carbohydrate diets
• 3/5 studies found Mediterranean diet better than others, 2/5 found similar
• Similar improvements in blood lipids, glycemic control, and BP
Mancini, Am J Med, 2016
The Paleolithic (Paleo) diet
• What is this diet?
• Mimic the way cavemen ate in the Stone Ages
• Foods include: vegetables, fruit, lean meats, poultry, fish, eggs, tofu, nuts and seeds
• Cannot eat: cereals, grains, legumes and dairy
• What does the science say?
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Small studies
Effective at reducing body weight and fat mass
Improvement in glycemic control, BP, lipids
Effects similar to traditional weight loss
• Potential harms
• Low in calcium
Pitt, Aug Fam Physician, 2016
Weight Watchers (and other commercial programs)
• What is this diet?
• Commercial weight loss program
• Can eat a certain amount of points from foods/day
• Online or group format - accountability
• What does the science say?
• Can induce weight loss
• Adherence is key
• Similar to other weight loss interventions
• Overall commercial programs are better than control to promote weight
loss
Thomas, Obesity, 2017; Dansinger, JAMA, 2005; Gudzune, Ann Intern Med, 2015
What do all of these diets have in common?
So which diet is best?
What does the science say?
• https://youtu.be/2T0El0v5VgI?t=1038
Johnston, JAMA, 2014
Weight loss diet: Summary
• There are many different weight loss diets with evidence to show they will help
you lose weight
• There is no magic diet – they all rely on you decreasing energy intake
• Evidence of long-term effectiveness and health outcomes is lacking for some
very restrictive diets
• Focusing on eating whole foods that promote satiety can help you adhere to
your chosen diet